Tier 1 (Desktop Analysis)

U.S. Fish & Wildlife Service

U.S. Fish and Wildlife Service
Land-Based Wind Energy Guidelines

Cover Photo:
Wind Turbine. Photo by Stefanie Stavrakas, USFWS

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
OMB Control No, 1018-0148
Expiration Date: 09/30/2012

U.S. Fish and Wildlife Service
Land-Based Wind Energy Guidelines

March 23, 2012
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Acknowledgements
The U.S. Fish and Wildlife Service (Service) would like to recognize and thank the Wind Turbine Guidelines
Advisory Committee for its dedication and preparation of its Recommendations. The Recommendations have served
as the basis from which the Service’s team worked to develop the Service’s Land-Based Wind Energy Guidelines.
The Service also recognizes the tireless efforts of the Headquarters, Regional and Field Office staff that helped to
review and update these Guidelines.

Paperwork Reduction Act Statement: The Land-Based Wind Energy Guidelines contain reporting and recordkeeping
requirements that require Office of Management and Budget approval in accordance with the Paperwork Reduction
Act of 1995. Your response is voluntary. We collect this information in order to provide technical assistance related
to addressing wildlife conservation concerns at all stages of land-based wind energy development. For each
response, we estimate the time necessary to provide the information as follows:
Tier 1 – 83 hours
Tier 2 – 375 hours
Tier 3 – 2,880 hours
Tier 4 – 2,550 hours
Tier 5 – 2,400 hours
The above estimates include time for reviewing instructions, gathering and maintaining data, and preparing and
transmitting reports. Send comments regarding these estimates or any other aspect of the requirements to the
Service Information Collection Clearance Officer, U.S. Fish and Wildlife Service, 4401 N. Fairfax Drive, MS 2042PDM, Arlington, VA 22203.
We may not conduct and you are not required to respond to a collection of information unless it displays a currently
valid OMB control number.
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Table of Contents
Executive Summary……………………………………………………………………………………………… vi
Chapter 1 - General Overview…………………………………………………………………………………… 1

Statutory Authorities……………………………………………………………………………………… 1

Migratory Bird Treaty Act……………………………………………………………………… 2
Bald and Golden Eagle Protection Act………………………………………………………… 2
Endangered Species Act……………………………………………………………………………3

Implementation of the Guidelines………………………………………………………………………… 4

Consideration of the Guidelines in MBTA and BGEPA Enforcement……………………… 6
Scope and Project Scale of the Guidelines……………………………………………………… 6
Service Review Period…………………………………………………………………………… 7

Introduction to the Decision Framework Using a Tiered Approach…………………………………… 7

Considering Risk in the Tiered Approach………………………………………………………………… 10

Cumulative Impacts of Project Development…………………………………………………………… 10

Other Federal Agencies…………………………………………………………………………………… 10

Relationship to Other Guidelines………………………………………………………………………… 11

Chapter 2: Tier 1 – Preliminary Site Evaluation………………………………………………………………… 12

Tier 1 Questions…………………………………………………………………………………………… 13

Tier 1 Methods and Metrics……………………………………………………………………………… 13

Tier 1 Decision Points……………………………………………………………………………………… 13

Chapter 3: Tier 2 – Site Characterization………………………………………………………………………… 14

Tier 2 Questions ………………………………………………………………………………………………14

Tier 2 Methods and Metrics…………………………………………………………………………… 15

Tier 2 Decision Points……………………………………………………………………………………… 18

Chapter 4: Tier 3 – Field Studies to Document Site Wildlife and Habitat and Predict Project Impacts………… 19

Tier 3 Questions …………………………………………………………………………………………… 19

Tier 3 Study Design Considerations……………………………………………………………………… 24

Assessing Presence……………………………………………………………………………… 24
Assessing Site Use/Behavior…………………………………………………………………… 24
Duration/Intensity of Studies…………………………………………………………………… 25
Assessing Risk to Species of Concern…………………………………………………………… 25

Tier 3 Technical Resources………………………………………………………………………………… 26

Tier 3, Question 1………………………………………………………………………………… 26
Tier 3, Question 2………………………………………………………………………………… 27
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Tier 3, Question 3………………………………………………………………………………… 28

Tier 3 Decision Points……………………………………………………………………………………… 33

Chapter 5: Tier 4 – Post-construction Studies to Estimate Impacts……………………………………………

34

34

Tier 4a – Fatality Studies…………………………………………………………………………………

Tier 4a Questions………………………………………………………………………………… 35
Tier 4a Protocol Design Considerations……………………………………………………… 35

Tier 4a Study Objectives…………………………………………………………………………………… 37

Tier 4b – Assessing direct and indirect impacts of habitat loss, degradation, and fragmentation…… 40

Tier 4b Protocol Design Considerations………………………………………………………… 41
Tier 4b Decision Points………………………………………………………………………… 41

Chapter 6: Tier 5 – Other Post-construction Studies …………………………………………………………… 43

Tier 5 Questions …………………………………………………………………………………………… 43

Tier 5 Study Design Considerations……………………………………………………………………… 44

Tier 5 Examples…………………………………………………………………………………
Tier 5 Studies and Research……………………………………………………………………

44
46

Chapter 7: Best Management Practices………………………………………………………………………… 49

Site Construction and Operation………………………………………………………………………… 49

Retrofitting, Repowering, and Decommissioning………………………………………………………

51

Retrofitting……………………………………………………………………………………… 51
Repowering……………………………………………………………………………………… 51
Decommissioning………………………………………………………………………………… 52

Chapter 8: Mitigation…………………………………………………………………………………………… 53

NEPA Guidance on Mitigation…………………………………………………………………………… 53

Compensatory Mitigation………………………………………………………………………………… 54

Migratory Birds and Eagles……………………………………………………………………………… 54

Endangered Species………………………………………………………………………………………

54

Chapter 9: Advancing Use, Cooperation and Effective Implementation………………………………………… 55

Conflict Resolution………………………………………………………………………………………… 55

Bird and Bat Conservation Strategies (BBCS)………………………………………………………… 55

Project Interconnection Lines…………………………………………………………………………… 55

Confidentiality of Site Evaluation Process as Appropriate……………………………………………

Collaborative Research…………………………………………………………………………………… 56

Service - State Coordination and Cooperation…………………………………………………………

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56

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Service Tribal Consultation and Coordination…………………………………………………………

57

Tribal Wind Energy Development on Reservation Lands…………………………………… 57
Tribal Wind Energy Development on Lands that are not held in Trust……………………… 57
Non-Tribal Wind Energy Development – Consultation with Indian Tribal Governments… 57

58

Non-Governmental Organization Actions………………………………………………………………

Non-Governmental Organization Conservation Lands………………………………………………… 58

Appendix A: Glossary…………………………………………………………………………………………… 59
Appendix B: Literature Cited…………………………………………………………………………………… 64
Appendix C: Sources of Information Pertaining to Methods to Assess Impacts to Wildlife…………………… 70
List of Figures and Tables

Table 1. Suggested Communications Protocol…………………………………………………………… 5

Figure 1. General Framework of Tiered Approach……………………………………………………… 9

Table 2. Decision Framework for Tier 4a Fatality Monitoring of Species of Concern.……………… 39

Table 3. Decision Framework to Guide Studies for Minimizing Impacts to Habitat and Species of
Habitat Fragmentation (HF) Concern.…………………………………………………………………… 42

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Executive Summary
As the Nation shifts to renewable
energy production to supplant the
need for carbon-based fuel, wind
energy will be an important source
of power. As wind energy production
increases, both developers and
wildlife agencies have recognized
the need for a system to evaluate
and address the potential negative
impacts of wind energy projects on
species of concern. These voluntary
Guidelines provide a structured,
scientific process for addressing
wildlife conservation concerns at all
stages of land-based wind energy
development. They also promote
effective communication among wind
energy developers and federal, state,
and local conservation agencies and
tribes. When used in concert with
appropriate regulatory tools, the
Guidelines form the best practical
approach for conserving species
of concern. The Guidelines have
been developed by the Interior
Department’s U.S. Fish and Wildlife
Service (Service) working with the
Wind Turbine Guidelines Advisory
Committee. They replace interim
voluntary guidance published by the
Service in 2003.
The Guidelines discuss various
risks to “species of concern” from
wind energy projects, including
collisions with wind turbines and
associated infrastructure; loss
and degradation of habitat from
turbines and infrastructure;
fragmentation of large habitat
blocks into smaller segments that
may not support sensitive species;
displacement and behavioral
changes; and indirect effects such
as increased predator populations
or introduction of invasive plants.
The Guidelines assist developers
in identifying species of concern
that may potentially be affected by
their proposed project, including
migratory birds; bats; bald and

1

golden eagles and other birds of
prey; prairie and sage grouse;
and listed, proposed, or candidate
endangered and threatened
species. Wind energy development
in some areas may be precluded
by federal law; other areas may
be inappropriate for development
because they have been recognized
as having high wildlife value based
on their ecological rarity and
intactness.
The Guidelines use a “tiered
approach” for assessing potential
adverse effects to species of concern
and their habitats. The tiered
approach is an iterative decisionmaking process for collecting
information in increasing detail;
quantifying the possible risks of
proposed wind energy projects
to species of concern and their
habitats; and evaluating those risks
to make siting, construction, and
operation decisions. During the
pre-construction tiers (Tiers 1, 2,
and 3), developers are working to
identify, avoid and minimize risks to
species of concern. During postconstruction tiers (Tiers 4 and 5),
developers are assessing whether
actions taken in earlier tiers to
avoid and minimize impacts are
successfully achieving the goals and,
when necessary, taking additional
steps to compensate for impacts.
Subsequent tiers refine and build
upon issues raised and efforts
undertaken in previous tiers. Each
tier offers a set of questions to help
the developer evaluate the potential
risk associated with developing a
project at the given location.
Briefly, the tiers address:
• Tier 1 – Preliminary site
evaluation (landscape-scale
screening of possible project
sites)

• Tier 2 – Site characterization
(broad characterization of one
or more potential project sites)
• Tier 3 – Field studies to
document site wildlife and
habitat and predict project
impacts
• Tier 4 – Post-construction
studies to estimate impacts1
• Tier 5 – Other postconstruction studies and
research
The tiered approach provides the
opportunity for evaluation and
decision-making at each stage,
enabling a developer to abandon or
proceed with project development,
or to collect additional information
if required. This approach does
not require that every tier, or
every element within each tier, be
implemented for every project.
The Service anticipates that many
distributed or community facilities
will not need to follow the Guidelines
beyond Tiers 1 and 2. Instead, the
tiered approach allows efficient use
of developer and wildlife agency
resources with increasing levels of
effort.
If sufficient data are available
at a particular tier, the following
outcomes are possible:
1. The project proceeds to the
next tier in the development
process without additional
data collection.
2. The project proceeds to the
next tier in the development
process with additional data
collection.
3. An action or combination
of actions, such as project

The Service anticipates these studies will include fatality monitoring as well as studies to evaluate habitat impacts.

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

modification, mitigation,
or specific post-construction
monitoring, is indicated.
4. The project site is abandoned
because the risk is considered
unacceptable.
If data are deemed insufficient
at a tier, more intensive study is
conducted in the subsequent tier
until sufficient data are available
to make a decision to modify the
project, proceed with the project, or
abandon the project.
The most important thing a
developer can do is to consult with
the Service as early as possible in
the development of a wind energy
project. Early consultation offers
the greatest opportunity for

avoiding areas where development
is precluded or where wildlife
impacts are likely to be high
and difficult or costly to remedy
or mitigate at a later stage. By
consulting early, project developers
can also incorporate appropriate
wildlife conservation measures and
monitoring into their decisions about
project siting, design, and operation.
Adherence to the Guidelines is
voluntary and does not relieve any
individual, company, or agency of
the responsibility to comply with
laws and regulations. However, if
a violation occurs the Service will
consider a developer’s documented
efforts to communicate with
the Service and adhere to the
Guidelines. The Guidelines include
a Communications Protocol which

provides guidance to both developers
and Service personnel regarding
appropriate communication and
documentation.
The Guidelines also provide
Best Management Practices for
site development, construction,
retrofitting, repowering, and
decommissioning. For additional
reference, a glossary of terms and
list of literature cited are included in
the appendices.

Wind Resource Map. Credit: NREL

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 1 - General Overview
The mission of the U.S. Fish and
Wildlife Service (Service) is working
with others to conserve, protect and
enhance fish, wildlife, plants and
their habitats for the continuing
benefit of the American people. As
part of this, the Service implements
statutes including the Endangered
Species Act, Migratory Bird Treaty
Act, and Bald and Golden Eagle
Protection Act. These statutes
prohibit taking of federally listed
species, migratory birds, and eagles
unless otherwise authorized.

(3)
Produce potentially

comparable data across the
Nation;

Recent studies have documented
that wind energy facilities can kill
birds and bats. Mortality rates
in fatalities per nameplate MW
per year vary among facilities and
regions. Studies have indicated that
relatively low raptor (e.g., hawks,
eagles) fatality rates exist at most
modern wind energy developments
with the exception of some facilities
in California and Wyoming. Turbinerelated bat deaths have been
reported at each wind facility to
date. Generally, studies in the West
have reported lower rates of bat
fatalities than facilities in the East.
There is still much uncertainty
regarding geographic distribution
and causes of bat fatalities (NWCC
2010).

As the United States moves to
expand wind energy production,
it also must maintain and protect
the Nation’s wildlife and their
habitats, which wind energy
production can negatively affect.
As with all responsible energy
development, wind energy projects
should adhere to high standards
for environmental protection. With
proper diligence paid to siting,
operations, and management of
projects, it is possible to mitigate
for adverse effects to wildlife,
and their habitats. This is best
accomplished when the wind energy
project developer communicates as
early as possible with the Service
and other stakeholders. Such
early communication allows for the
greatest range of development and
mitigation options. The following
website contains contact information
for the Service Regional and Field
offices as well as State wildlife
agencies: http://www.fws.gov/offices/
statelinks.html.

These Guidelines are intended to:
(1)

Promote compliance
with relevant wildlife laws
and regulations;

(2)

Encourage scientifically
rigorous survey, monitoring,
assessment, and research
designs proportionate to the
risk to species of concern;

(4)

Mitigate, including avoid,
minimize, and compensate
for potential adverse effects
on species of concern and
their habitats; and,

(5)

Improve the ability to
predict and resolve effects
locally, regionally, and
nationally.

In response to increasing wind
energy development in the United
States, the Service released a set
of voluntary, interim guidelines for

reducing adverse effects to fish and
wildlife resources from wind energy
projects for public comment in July
2003. After the Service reviewed the
public comments, the Secretary of
the Interior (Secretary) established
a Federal Advisory Committee2 to
provide recommendations to revise
the guidelines related to landbased wind energy facilities. In
March 2007, the U.S. Department
of the Interior established the
Wind Turbine Guidelines Advisory
Committee (the Committee).
The Committee submitted its
final Recommended Guidelines
(Recommendations) to the Secretary
on March 4, 2010. The Service used
the Recommendations to develop
its Land-Based Wind Energy
Guidelines.
The Service encourages project
proponents to use the process
described in these voluntary Landbased Wind Energy Guidelines
(Guidelines) to address risks to
species of concern. The Service
intends that these Guidelines, when
used in concert with the appropriate
regulatory tools, will form the best
practical approach for conservation
of species of concern.

Statutory Authorities
These Guidelines are not intended
nor shall they be construed to
limit or preclude the Service from
exercising its authority under any
law, statute, or regulation, or from
conducting enforcement action
against any individual, company,
or agency. They are not meant to
relieve any individual, company, or
agency of its obligations to comply
with any applicable federal, state,

2
Committee membership, from 2008 to 2011, has included: Taber Allison, Massachusetts Audubon; Dick Anderson, California Energy
Commission; Ed Arnett, Bat Conservation International; Michael Azeka, AES Wind Generation; Thomas Bancroft, National Audubon; Kathy
Boydston, Texas Parks and Wildlife Department; René Braud, EDP Renewables; Scott Darling, Vermont Fish and Wildlife Department; Michael
Daulton, National Audubon; Aimee Delach, Defenders of Wildlife; Karen Douglas, California Energy Commission; Sam Enfield, MAP Royalty;
Greg Hueckel, Washington Department of Fish and Wildlife; Jeri Lawrence, Blackfeet Nation; Steve Lindenberg, U.S. Department of Energy;
Andy Linehan, Iberdrola Renewables; Rob Manes, The Nature Conservancy, Kansas; Winifred Perkins, NextEra Energy Resources; Steven
Quarles, Crowell & Moring; Rich Rayhill, Ridgeline Energy; Robert Robel, Kansas State University; Keith Sexson, Association of Fish and
Wildlife Agencies; Mark Sinclair, Clean Energy States Alliance; David Stout, U.S. Fish and Wildlife Service; Patrick Traylor, Hogan Lovells.

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

tribal, or local laws, statutes, or
regulations. The Guidelines do not
prevent the Service from referring
violations of law for enforcement
when a company has not followed the
Guidelines.
Ultimately it is the responsibility
of those involved with the planning,
design, construction, operation,
maintenance, and decommissioning
of wind projects to conduct relevant
wildlife and habitat evaluation and
determine, which, if any, species
may be affected. The results of
these analyses will inform all efforts
to achieve compliance with the
appropriate jurisdictional statutes.
Project proponents are responsible
for complying with applicable state
and local laws.
Migratory Bird Treaty Act
The Migratory Bird Treaty Act
(MBTA) is the cornerstone of
migratory bird conservation and
protection in the United States. The
MBTA implements four treaties that
provide for international protection
of migratory birds. It is a strict
liability statute, meaning that proof
of intent, knowledge, or negligence
is not an element of an MBTA
violation. The statute’s language
is clear that actions resulting in a
“taking” or possession (permanent
or temporary) of a protected species,
in the absence of a Service permit
or regulatory authorization, are a
violation of the MBTA.
The MBTA states, “Unless and
except as permitted by regulations
… it shall be unlawful at any time,
by any means, or in any manner
to pursue, hunt, take, capture, kill
… possess, offer for sale, sell …
purchase … ship, export, import …
transport or cause to be transported
… any migratory bird, any part,
nest, or eggs of any such bird ….
[The Act] prohibits the taking,
killing, possession, transportation,
import and export of migratory
birds, their eggs, parts, and nests,
except when specifically authorized
by the Department of the Interior.”
16 U.S.C. 703. The word “take” is
defined by regulation as “to pursue,
2 

hunt, shoot, wound, kill, trap,
capture, or collect, or attempt to
pursue, hunt, shoot, wound, kill, trap,
capture, or collect.” 50 CFR 10.12.
The MBTA provides criminal
penalties for persons who commit
any of the acts prohibited by the
statute in section 703 on any of the
species protected by the statute.
See 16 U.S.C. 707. The Service
maintains a list of all species
protected by the MBTA at 50 CFR
10.13. This list includes over one
thousand species of migratory birds,
including eagles and other raptors,
waterfowl, shorebirds, seabirds,
wading birds, and passerines. The
MBTA does not protect introduced
species such as the house (English)
sparrow, European starling, rock
dove (pigeon), Eurasian collareddove, and non-migratory upland
game birds. The Service maintains
a list of introduced species not
protected by the Act. See 70 Fed.
Reg. 12,710 (Mar. 15, 2005).
Bald and Golden Eagle Protection
Act

either a decrease in productivity or
nest abandonment by substantially
interfering with normal breeding,
feeding, or sheltering behavior. 50
CFR 22.3. BGEPA authorizes the
Service to permit the take of eagles
for certain purposes and under
certain circumstances, including
scientific or exhibition purposes,
religious purposes of Indian tribes,
and the protection of wildlife,
agricultural, or other interests, so
long as that take is compatible with
the preservation of eagles. 16 U.S.C.
668a.
In 2009, the Service promulgated
a final rule on two new permit
regulations that, for the first
time, specifically authorize the
incidental take of eagles and eagle
nests in certain situations under
BGEPA. See 50 CFR 22.26 &
22.27. The permits authorize
limited, non-purposeful (incidental)
take of bald and golden eagles;
authorizing individuals, companies,
government agencies (including
tribal governments), and other
organizations to disturb or
otherwise take eagles in the course
of conducting lawful activities such
as operating utilities and airports.

Under authority of the Bald and
Golden Eagle Protection Act
(BGEPA), 16 U.S.C.
668–668d, bald eagles and
golden eagles are afforded
additional legal protection.
BGEPA prohibits the take,
sale, purchase, barter,
offer of sale, purchase, or
barter, transport, export
or import, at any time or
in any manner of any bald
or golden eagle, alive or
dead, or any part, nest, or
egg thereof. 16 U.S.C. 668.
BGEPA also defines take
to include “pursue, shoot,
shoot at, poison, wound,
kill, capture, trap, collect,
molest, or disturb,” 16
U.S.C. 668c, and includes
criminal and civil penalties
for violating the statute.
See 16 U.S.C. 668. The
Service further defined the
term “disturb” as agitating
or bothering an eagle to a
degree that causes, or is
likely to cause, injury, or
Bald Eagle, Credit:

USFWS

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Removal of active eagle nests would
usually be allowed only when it is
necessary to protect human safety or
the eagles. Removal of inactive nests
can be authorized when necessary
to ensure public health and safety,
when a nest is built on a humanengineered structure rendering it
inoperable, and when removal is
necessary to protect an interest
in a particular locality, but only if
the take or mitigation for the take
will provide a clear and substantial
benefit to eagles.
To facilitate issuance of permits
under these new regulations,
the Service has drafted Eagle
Conservation Plan (ECP) Guidance.
The ECP Guidance is compatible
with these Land-Based Wind
Energy Guidelines. The Guidelines
guide developers through the
process of project development and
operation. If eagles are identified
as a potential risk at a project site,
developers are strongly encouraged
to refer to the ECP Guidance. The
ECP Guidance describes specific
actions that are recommended
to comply with the regulatory
requirements in BGEPA for an eagle
take permit, as described in 50 CFR
22.26 and 22.27. The ECP Guidance
provides a national framework for
assessing and mitigating risk specific
to eagles through development of
ECPs and issuance of programmatic
incidental takes of eagles at wind
turbine facilities. The Service
will make its final ECP Guidance
available to the public through its
website.
Endangered Species Act
The Endangered Species Act (16
U.S.C. 1531–1544; ESA) was enacted
by Congress in 1973 in recognition
that many of our Nation’s native
plants and animals were in danger of
becoming extinct. The ESA directs
the Service to identify and protect
these endangered and threatened
species and their critical habitat, and
to provide a means to conserve their
ecosystems. To this end, federal
agencies are directed to utilize
their authorities to conserve listed
species, and ensure that their actions

Indiana bat. Credit: USFWS

are not likely to jeopardize the
continued existence of these species
or destroy or adversely modify their
critical habitat. Federal agencies
are encouraged to do the same with
respect to “candidate” species that
may be listed in the near future. The
law is administered by the Service
and the Commerce Department’s
National Marine Fisheries Service
(NMFS). For information regarding
species protected under the ESA,
see: http://www.fws.gov/endangered/.
The Service has primary
responsibility for terrestrial and
freshwater species, while NMFS
generally has responsibility
for marine species. These two
agencies work with other agencies
to plan or modify federal projects
so that they will have minimal
impact on listed species and their
habitats. Protection of species is
also achieved through partnerships
with the states, through federal
financial assistance and a system of
incentives available to encourage
state participation. The Service
also works with private landowners,
providing financial and technical
assistance for management

actions on their lands to benefit both
listed and non-listed species.
Section 9 of the ESA makes it
unlawful for a person to “take” a
listed species. Take is defined as “...
to harass, harm, pursue, hunt, shoot,
wound, kill, trap, capture, or collect
or attempt to engage in any such
conduct.” 16 U.S.C. 1532(19). The
terms harass and harm are further
defined in our regulations. See 50
CFR 17.3. However, the Service
may authorize “incidental take”
(take that occurs as a result of an
otherwise legal activity) in two ways.
Take of federally listed species
incidental to a lawful activity may
be authorized through formal
consultation under section 7(a)(2) of
the ESA, whenever a federal agency,
federal funding, or a federal permit
is involved. Otherwise, a person may
seek an incidental take permit under
section 10(a)(1)(B) of the ESA upon
completion of a satisfactory habitat
conservation plan (HCP) for listed
species. Developers not receiving
federal funding or authorization
should contact the Service to obtain
an incidental take permit if a wind
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

information with the Service and
considered its advice.
• For projects initiated prior to
publication, the developer should
consider where they are in the
planning process relative to the
appropriate tier and inform the
Service of what actions they will
take to apply the Guidelines.
• For projects operating at the
time of publication, the developer
should confer with the Service
regarding the appropriate period
of fatality monitoring consistent
with Tier 4, communicate and
share information with the
Service on monitoring results,
and consider Tier 5 studies
and mitigation options where
appropriate.
Utility-Scale Wind turbine with an anemometer
tower in the background. Credit: University of
Minnesota College of Science and Engineering

energy project is likely to result
in take of listed threatened or
endangered wildlife species. For
more information regarding formal
consultation and the requirements
of obtaining HCPs, please see the
Endangered Species Consultation
Handbook at http://www.fws.gov/
endangered/esa-library/index.
html#consultations and the
Service’s HCP website, http://www.
fws.gov/endangered/what-we-do/
hcp-overview.html.

Implementation of the Guidelines
Because these Guidelines are
voluntary, the Service encourages
developers to use them as soon
as possible after publication. To
receive the considerations discussed
on page 6 regarding enforcement
priorities, a wind energy project
would fall into one of three general
categories relative to timing and
implementation:
• For projects initiated after
publication, the developer has
applied the Guidelines, including
the tiered approach, through site
selection, design, construction,
operation and post-operation
phases of the project, and has
communicated and shared
4 

Projects that are already under
development or are in operation
are not expected to start over or
return to the beginning of a specific
tier. Instead, these projects should
implement those portions of the
Guidelines relevant to the current
phases of the project per the bullets
above.
The Service is aware that it will
take time for Service staff and
other personnel, including wind
energy developers and their
biologists, to develop expertise
in the implementation of these
Guidelines. Service staff and many
staff associated with the wind
energy industry have been involved
with developing these Guidelines.
Therefore, they have a working
knowledge of the Guidelines. To
further refine their training, the
Service will make every effort to
offer an in-depth course within 6
months of the final Guidelines being
published.
The Communications Protocol on
page 5 provides guidance to Service
staff and developers in the exchange
of information and recommendations
at each tier in the process. Although
the advice of the Service is not
binding, a developer should review
such advice, and either accept or
reject it. If they reject it, they

should contemporaneously document
with reasoned justification why they
did so. Although the Guidelines
leave decisions up to the developer,
the Service retains authority to
evaluate whether developer efforts
to mitigate impacts are sufficient,
to determine significance, and to
refer for prosecution any unlawful
take that it believes to be reasonably
related to lack of incorporation
of Service recommendations or
insufficient adherence with the
Guidelines.

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Table 1. Suggested Communications Protocol
This table provides examples of potential communication opportunities between a wind energy project developer and
the Service. Not all projects will follow all steps indicated below.
TIER

Project Developer/Operator Role

Service Role

Tier 1:
Preliminary site
evaluation

• Landscape level assessment of habitat for
species of concern
• Request data sources for existing information
and literature

• Provide lists of data sources and references,
if requested

Tier 2: Site
characterization

• Assess potential presence of species of
concern, including species of habitat
fragmentation concern, likely to be on site
• Assess potential presence of plant
communities present on site that may provide
habitat for species of concern
• Assess potential presence of critical
congregation areas for species of concern
• One or more reconnaissance level site visit by
biologist
• Communicate results of site visits and other
assessments with the Service
• Provide general information about the size
and location of the project to the Service

• Provide species lists, for species of concern,
including species of habitat fragmentation
concern, for general area, if available
• Provide information regarding plant
communities of concern, if available
• Respond to information provided about
findings of biologist from site visit
• Identify initial concerns about site(s) based
on available information
• Inform lead federal agencies of
communications with wind project
developers

Tier 3: Field
studies and impact
prediction

• Discuss extent and design of field studies to
conduct with the Service
• Conduct biological studies
• Communicate results of all studies to Service
field office in a timely manner
• Evaluate risk to species of concern from
project construction and operation
• Identify ways to mitigate potential direct and
indirect impacts of building and operating the
project

• Respond to requests to discuss field studies
• Advise project proponent about studies to
conduct and methods for conducting them
• Communicate with project proponent(s)
about results of field studies and risk
assessments
• Communicate with project proponents(s)
ways to mitigate potential impacts of
building and operating the project
• Inform lead federal agencies of
communications with wind project
developers

Tier 4: Post
construction
studies to estimate
impacts

• Discuss extent and design of post-construction
studies to conduct with the Service
• Conduct post-construction studies to assess
fatalities and habitat-related impacts
• Communicate results of all studies to Service
field office in a timely manner
• If necessary, discuss potential mitigation
strategies with Service
• Maintain appropriate records of data collected
from studies

• Advise project operator on study design,
including duration of studies to collect
adequate information
• Communicate with project operator about
results of studies
• Advise project operator of potential
mitigation strategies, when appropriate

Tier 5: Other
post-construction
studies and
research

• Communicate with the Service about the need
for and design of other studies and research to
conduct with the Service, when appropriate,
particularly when impacts exceed predicted
levels
• Communicate with the Service about ways
to evaluate cumulative impacts on species
of concern, particularly species of habitat
fragmentation concern
• Conduct appropriate studies as needed
• Communicate results of studies with the
Service
• Identify potential mitigation strategies to
reduce impacts and discuss them with the
Service

• Advise project proponents as to need for
Tier 5 studies to address specific topics,
including cumulative impacts, based on
information collected in Tiers 3 and 4
• Advise project proponents of methods and
metrics to use in Tier 5 studies
• Communicate with project operator and
consultants about results of Tier 5 studies
• Advise project operator of potential
mitigation strategies, when appropriate,
based on Tier 5 studies

 5

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Consideration of the Guidelines in
MBTA and BGEPA Enforcement
The Service urges voluntary
adherence to the Guidelines and
communication with the Service
when planning and operating a
facility. While it is not possible to
absolve individuals or companies
from MBTA or BGEPA liability, the
Office of Law Enforcement focuses
its resources on investigating
and prosecuting those who take
migratory birds without identifying
and implementing reasonable and
effective measures to avoid the
take. The Service will regard a
developer’s or operator’s adherence
to these Guidelines, including
communication with the Service, as
appropriate means of identifying
and implementing reasonable and
effective measures to avoid the
take of species protected under the
MBTA and BGEPA.3 The Chief of
Law Enforcement or more senior
official of the Service will make
any decision whether to refer for
prosecution any alleged take of such
species, and will take such adherence
and communication fully into account
when exercising discretion with
respect to such potential referral.
Each developer or operator will be
responsible for maintaining internal
records sufficient to demonstrate
adherence to the Guidelines and
response to communications from
the Service. Examples of these
records could include: studies
performed in the implementation of
the tiered approach; an internal or
external review or audit process; a
bird and bat conservation strategy;
or a wildlife management plan.
If a developer and operator are not
the same entity, the Service expects
the operator to maintain sufficient
records to demonstrate adherence to
the Guidelines.
Scope and Project Scale of the
Guidelines
The Guidelines are designed for
“utility-scale” land-based wind

3

Communication with Christy Johnson-Hughes. Credit: Rachel London, USFWS

energy projects to reduce potential
impacts to species of concern,
regardless of whether they are
proposed for private or public
lands. A developer of a distributed
or community scale wind project
may find it useful to consider the
general principles of the tiered
approach to assess and reduce
potential impacts to species of
concern, including answering Tier
1 questions using publicly available
information. In the vast majority
of situations, appropriately sited
small wind projects are not likely to
pose significant risks to species of
concern. Answering Tier 1 questions
will assist a developer of distributed
or community wind projects, as well
as landowners, in assessing the need
to further communicate with the
Service, and precluding, in many
cases, the need for full detailed
pre-construction assessments or
monitoring surveys typically called
for in Tiers 2 and 3. If landowners
or community/distributed wind
developers encounter problems
locating information about specific
sites they can contact the Service
and/or state wildlife agencies to
determine potential risks to species
of concern for their particular
project.

The tiered approach is designed
to lead to the appropriate amount
of evaluation in proportion to
the anticipated level of risk that
a project may pose to species
of concern and their habitats.
Study plans and the duration and
intensity of study efforts should
be tailored specifically to the
unique characteristics of each site
and the corresponding potential
for significant adverse impacts
on species of concern and their
habitats as determined through
the tiered approach. This is why
the tiered approach begins with
an examination of the potential
location of the project, not the size
of the project. In all cases, study
plans and selection of appropriate
study methods and techniques may
be tailored to the relative scale,
location, and potential for significant
adverse impacts of the proposed site.
The Service considers a “project”
to include all phases of wind
energy development, including,
but not limited to, prospecting, site
assessment, construction, operation,
and decommissioning, as well as
all associated infrastructure and
interconnecting electrical lines.
A “project site” is the land and
airspace where development occurs

With regard to eagles, this paragraph will only apply when a project is not likely to result in take. If Tiers 1, 2, and/or 3 identify a potential to
take eagles, developers should consider developing an ECP and, if necessary, apply for a take permit

6 

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
or is proposed to occur, including
the turbine pads, roads, power
distribution and transmission
lines on or immediately adjacent
to the site; buildings and related
infrastructure, ditches, grades,
culverts; and any changes or
modifications made to the original
site before development occurs.
Project evaluations should consider
all potential effects to species of
concern, which includes species 1)
protected by the MBTA, BGEPA, or
ESA (including candidate species),
designated by law, regulation or
other formal process for protection
and/or management by the relevant
agency or other authority, or that
have been shown to be significantly
adversely affected by wind energy
development; and 2) determined to
be possibly affected by the project.
These Guidelines are not designed to
address power transmission beyond
the point of interconnection to the
transmission system.
Service Review Period
The Service is committed to
providing timely responses.
Service Field Offices should
typically respond to requests
by a wind energy developer for
information and consultation on
proposed site locations (Tiers 1
and 2), pre- and post-construction
study designs (Tiers 3 and 4), and
proposed mitigation (Tier 3) within
60 calendar days. The request
should be in writing to the Field
Office and copied to the Regional
Office with information about
the proposed project, location(s)
under consideration, and point of
contact. The request should contain
a description of the information
needed from the Service. The
Service will provide a response,
even if it is to notify a developer of
additional review time, within the
60 calendar day review period. If
the Service does not respond within
60 calendar days of receipt of the
document, then the developer can
proceed through Tier 3 without
waiting for Service input. If the
Service provides comments at a
4

later time, the developer should
incorporate the comments if feasible.
It is particularly important that if
data from Tier 1-3 studies predict
that the project is likely to produce
significant adverse impacts on
species of concern, the developer
inform the Service of the actions it
intends to implement to mitigate
those impacts. If the Service cannot
respond within 60 calendar days,
this does not relieve developers from
their MBTA, BGEPA, and ESA
responsibilities.
The tiered approach allows a
developer in certain limited
circumstances to move directly from
Tier 2 to construction (e.g., adequate
survey data for the site exists). The
developer should notify the Service
of this decision and give the Service
60 calendar days to comment on the
proposed project prior to initiating
construction activities.

Introduction to the Decision
Framework Using a Tiered Approach
The tiered approach provides a
decision framework for collecting
information in increasing detail to
evaluate risk and make siting and
operational decisions. It provides
the opportunity for evaluation
and decision-making at each tier,
enabling a developer to proceed with
or abandon project development,
or to collect additional information
if necessary. This approach does
not require that every tier, or
every element within each tier, be
implemented for every project.
Instead, it allows efficient use of
developer and wildlife agency
resources with increasing levels of
effort until sufficient information and
the desired precision is acquired for
the risk assessment.
Figure 1 (“General Framework of
Tiered Approach”) illustrates the
tiered approach, which consists of up
to five iterative stages, or tiers:
• Tier 1 – Preliminary site
evaluation (landscape-scale
screening of possible project
sites)

• Tier 2 – Site characterization
(broad characterization of one or
more potential project sites)
• Tier 3 – Field studies to document
site wildlife and habitat and
predict project impacts
• Tier 4 – Post-construction studies
to estimate impacts4
• Tier 5 – Other post-construction
studies and research
At each tier, potential issues
associated with developing or
operating a project are identified
and questions formulated to guide
the decision process. Chapters Two
through Six outline the questions to
be posed at each tier, and describe
recommended methods and metrics
for gathering the data needed to
answer those questions.
The first three tiers correspond
to the pre-construction evaluation
phase of wind energy development.
At each of the three tiers, the
Guidelines provide questions that
developers should answer, followed
by recommended methods and
metrics to use in answering the
questions. Some questions are
repeated at each tier, with successive
tiers requiring a greater investment
in data collection to answer certain
questions. For example, while Tier
2 investigations may discover some
existing information on federal or
state-listed species and their use of
the proposed development site, it
may be necessary to collect empirical
data in Tier 3 studies to determine
the presence of federal or statelisted species.
Developers decide whether to
proceed to the next tier. Timely
communication and sharing of
information will allow opportunities
for the Service to provide, and
developers to consider, technical
advice. A developer should base the
decision on the information obtained
from adequately answering the
questions in this tier, whether the
methods used were appropriate for
the site selected, and the resulting

The Service anticipates these studies will include fatality monitoring as well as studies to evaluate habitat impacts.

 7

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
measure is in how well it helps meet
environmental, social, and economic
goals, increases scientific knowledge,
and reduces tensions among
stakeholders.”
This definition gives special
emphasis to uncertainty about
management effects, iterative
learning to reduce uncertainty, and
improved management as a result
of learning. The DOI Adaptive
Management Technical Guide is
located on the web at: www.doi.gov/
initiatives/AdaptiveManagement/
index.html.

Wind turbines in California. Credit: Rachel London, USFWS

assessment of risk posed to species
of concern and their habitats.
If sufficient data are available
at a particular tier, the following
outcomes are possible:
1. The project proceeds to the next
tier in the development process
without additional data collection.
2. The project proceeds to the next
tier in the development process
with additional data collection.
3. An action or combination
of actions, such as project
modification, mitigation, or specific
post-construction monitoring, is
indicated.
4. The project site is abandoned
because the risk is considered
unacceptable.
If data are deemed insufficient
at a tier, more intensive study is
conducted in the subsequent tier
until sufficient data are available
to make a decision to modify the
project, proceed with the project, or
abandon the project.
The tiered approach used in
these Guidelines embodies
adaptive management by
collecting increasingly detailed
information that is used to make
decisions about project design,
8 

construction, and operation as
the developer progresses through
the tiers. Adaptive management
is an iterative learning process
producing improved understanding
and improved management over
time (Williams et al 2007). DOI
has determined that its resource
agencies, and the natural resources
they oversee, could benefit from
adaptive management. Use of
adaptive management in DOI
is guided by the DOI Policy on
Adaptive Management. DOI has
adopted the National Research
Council’s 2004 definition of adaptive
management, which states:
“Adaptive management promotes
flexible decision making that
can be adjusted in the face of
uncertainties as outcomes from
management actions and other
events become better understood.
Careful monitoring of these
outcomes both advances scientific
understanding and helps adjust
policies or operations as part of an
iterative learning process. Adaptive
management also recognizes the
importance of natural variability in
contributing to ecological resilience
and productivity. It is not a ‘trial
and error’ process, but rather
emphasizes learning while doing.
Adaptive management does not
represent an end in itself, but rather
a means to more effective decisions
and enhanced benefits. Its true

No …………………………………………………………………………proceed to Tier 2
Unknown - Insufficient or inconclusive data …….……proceed to Tier 2
Yes………………………………………………abandon site or proceed to Tier 2

Unknown - Insufficient or inconclusive data ………….proceed to Tier 3
Low……………proceed to obtain state and local permit (if required),
design, and construction following BMPs
Moderate ………………………….…………….proceed to Tier 3 and mitigate
High, and:
a. can be adequately mitigated...modify project and proceed to Tier 3
b. cannot be adequately mitigated..………………………...abandon project

a.
b.

a.
b.

Low ……………………………………………..……………………….proceed to Tier 4
Moderate to high, and:
certainty regarding mitigation ………………………...... proceed to Tier 4
uncertainty regarding mitigation …………………………proceed to Tier 4
High, and:
can be adequately mitigated………..……………………..proceed to Tier 4
cannot be adequately mitigated …………..modify or abandon project

3.

2.

1.

Documented fatalities are equal to or lower than
predicted……………...…no further studies or mitigation needed
Documented fatalities are higher than predicted, but not significant,
and:
a. comparable data are available that support findings of not
significant……………………………………………....no further studies needed
b. comparable data not available to support findings of not
significant……………..additional year(s) of monitoring recommended
Documented fatalities are higher than predicted and are
significant………………………………………………..communicate with Service

TIER 4a (See Table 2, pg 39)
A. Tier 3 studies indicate low probability of significant adverse impacts

3.

1.
2.

TIER 3
A. Probability of significant adverse impacts?

3.
4.

1.
2.

TIER 2
A. Probability of significant adverse impacts?

1.
2.
3.

TIER 1
A. Species of concern known to be present?

Figure 1. General Framework of Tiered Approach

1.
2.

3.

2.

Documented fatalities are less than predicted and are not
significant,
and
no
ESA
or
BGEPA
species
are
affected………………..….....no further monitoring or mitigation needed
Documented fatalities are less than predicted but are still significant,
and no ESA or BGEPA species are affected…………………further
monitoring or mitigation needed
Fatalities are equal to or greater than predicted and are significant
OR ESA or BGEPA species are affected……………..…..communicate
with Service regarding additional mitigation

Documented fatalities are lower than or no different predicted, and:
are not significant and no ESA or BGEPA species are
affected ………….………….no further monitoring or mitigation needed
b. are
significant
OR
ESA
or
BGEPA
species
are
affected ....................................................communicate with Service
Documented fatalities are greater than predicted and are likely to be
species
are
significant
OR
ESA
or
BGEPA
affected.……………………………………….…………communicate with Service

a.

Tier 3 studies indicate high probability of significant adverse impacts
1.

2.

1.

Tier 3 studies indicate moderate probability of significant adverse
impacts

No…………………………………………………………….no further studies needed
Yes, and:
a. Tier 3 studies do not confirm presence…no further studies needed
b. Tier 3 studies confirm presence, but no significant adverse
impacts predicted, and:
i. Tier 4b studies confirm Tier 3 predictions…..………….….no further
studies or mitigation needed
ii. Tier 4b studies indicate potentially significant adverse
impacts ……………….Tier 5 studies and mitigation may be needed
c. Tier 3 studies confirm presence, and significant adverse impacts
predicted and mitigation plan is developed and implemented,
and:
i. Tier 4b studies determine mitigation is effective ………………….no
further studies or mitigation needed
ii. Tier 4b studies determine mitigation not effective………...further
mitigation and, where appropriate, Tier 5 studies needed

TIER 4b (See Table 3, pg. 42)
A. Species of habitat fragmentation concern potentially present?

C.

B.

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

 9

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Considering Risk in the Tiered
Approach
In the context of these Guidelines,
risk refers to the likelihood that
adverse impacts will occur to
individuals or populations of species
of concern as a result of wind
energy development and operation.
Estimates of fatality risk can be
used in a relative sense, allowing
comparisons among projects,
alternative development designs,
and in the evaluation of potential risk
to populations. Because there are
relatively few methods available for
direct estimation of risk, a weightof-evidence approach is often used
(Anderson et al. 1999). Until such
time that reliable risk predictive
models are developed regarding
avian and bat fatality and wind
energy projects, estimates of risk
would typically be qualitative, but
should be based upon quantitative
site information.
For the purposes of these
Guidelines, risk can also be defined
in the context of populations, but
that calculation is more complicated
as it could involve estimating the
reduction in population viability
as indicated by demographic
metrics such as growth rate, size
of the population, or survivorship,
either for local populations,
metapopulations, or entire species.
For most populations, risk cannot
easily be reduced to a strict
metric, especially in the absence of
population viability models for most
species. Consequently, estimating
the quantitative risk to populations
is usually beyond the scope of
project studies due to the difficulties
in evaluating these metrics, and
therefore risk assessment will be
qualitative.
Risk to habitat is a component of the
evaluation of population risk. In this
context, the estimated loss of habitat
is evaluated in terms of the potential
for population level effects (e.g.,
reduced survival or reproduction).
The assessment of risk should
synthesize sufficient data collected
at a project to estimate exposure
and predict impact for individuals
and their habitats for the species
10 

of concern, with what is known
about the population status of these
species, and in communication with
the relevant wildlife agency and
industry wildlife experts. Predicted
risk of these impacts could provide
useful information for determining
appropriate mitigation measures
if determined to be necessary. In
practice in the tiered approach, risk
assessments conducted in Tiers 1
and 2 require less information to
reach a risk-based decision than
those conducted at higher tiers.

Cumulative Impacts of Project
Development
Cumulative impacts are the
comprehensive effect on the
environment that results from the
incremental impact of a project
when added to other past, present,
and reasonably foreseeable
future actions. Developers are
encouraged to work closely with
federal and state agencies early
in the project planning process to
access any existing information
on the cumulative impacts of
individual projects on species and
habitats at risk, and to incorporate
it into project development and
any necessary wildlife studies. To
achieve that goal, it is important
that agencies and organizations take
the following actions to improve
cumulative impacts analysis:
• review the range of developmentrelated significant adverse
impacts;
• determine which species of
concern or their habitats within
the landscape are most at risk of
significant adverse impacts from
wind development in conjunction
with other reasonably foreseeable
significant adverse impacts; and
• make that data available for
regional or landscape level
analysis.
The magnitude and extent of the
impact on a resource depend on
whether the cumulative impacts
exceed the capacity for resource
sustainability and productivity.

For projects that require a federal
permit, funding, or other federal
nexus, the lead federal agency is
required to include a cumulative
impacts analysis in their National
Environmental Policy Act (NEPA)
review. The federal action agency
coordinates with the developer to
obtain the necessary information for
the NEPA review and cumulative
impacts analysis. To avoid project
delays, federal and state agencies
are encouraged to use existing
wildlife data for the cumulative
impacts analysis until improved data
are available.
Where there is no federal nexus,
individual developers are not
expected to conduct their own
cumulative impacts analysis.
However, a cumulative impacts
analysis would help developers
and other stakeholders better
understand the significance of
potential impacts on species of
concern and their habitats.

Other Federal Agencies
Other federal agencies, such as
the Bureau of Land Management,
National Park Service, U.S.
Department of Agriculture Forest
Service and Rural Utility Service,
Federal Energy Regulatory
Commission and Department of
Energy are often interested in
and involved with wind project
developments. These agencies
have a variety of expertise and
authorities they implement. Wind
project developers on public lands
will have to comply with applicable
regulations and policies of those
agencies. State and local agencies
and Tribes also have additional
interests and knowledge. The
Service recommends that, where
appropriate, wind project developers
contact these agencies early in the
tiered process and work closely with
them throughout project planning
and development to assure that
projects address issues of concern
to those agencies. The definition
of “species of concern” in these
Guidelines includes species which
are trust resources of States and
of federal agencies (See Glossary).
In those instances where a project
may significantly affect State trust

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
resources, wind energy developers
should work closely with appropriate
State agencies.

Relationship to Other Guidelines
These Guidelines replace the
Service’s 2003 interim voluntary
guidelines. The Service intends
that these Guidelines, when used
in concert with the appropriate
regulatory tools, will form the best
practical approach for conservation
of species of concern. For instance,
when developers find that a project

may affect an endangered or
threatened species, they should
comply with Section 7 or 10 of
the ESA to obtain incidental take
authorization. Other federal,
state, tribal and local governments
may use these Guidelines to
complement their efforts to address
wind energy development/wildlife
interactions. They are not intended
to supplant existing regional or
local guidance, or landscape-scale
tools for conservation planning,
but were developed to provide a
means of improving consistency

with the goals of the wildlife statutes
that the Service is responsible for
implementing. The Service will
continue to work with states, tribes,
and other local stakeholders on
map-based tools, decision-support
systems, and other products to
help guide future development and
conservation. Additionally, project
proponents should utilize any
relevant guidance of the appropriate
jurisdictional entity, which will
depend on the species and resources
potentially affected by proposed
development.

Pronghorn Antelope. Credit: Steve Hillebrand, USFWS

  11

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 2: Tier 1 – Preliminary Site Evaluation
For developers taking a first look
at a broad geographic area, a
preliminary evaluation of the general
ecological context of a potential
site or sites can serve as useful
preparation for working with the
federal, state, tribal, and/or local
agencies. The Service is available
to assist wind energy project
developers to identify potential
wildlife and habitat issues and should
be contacted as early as possible
in the company's planning process.
With this internal screening process,
the developer can begin to identify
broad geographic areas of high
sensitivity due to the presence
of: 1) large blocks of intact native
landscapes; 2) intact ecological
communities; 3) fragmentationsensitive species' habitats; or 4)
other important landscape-scale
wildlife values.
Tier 1 may be used in any of the
following three ways:
1. To identify regions where wind
energy development poses
significant risks to species
of concern or their habitats,
including the fragmentation of
large-scale habitats and threats to
regional populations of federal- or
state-listed species.

to be studied further to determine
if the site can be developed without
significant adverse impacts to
the species of concern or local
population(s). This may facilitate
discussions with the federal,
state, tribal, and/or local agencies
in a region being considered for
development. In some cases, Tier 1
studies could reveal serious concerns
indicating that a site should not be
developed.
Developers of distributed or
community scale wind projects
are typically considering limited
geographic areas to install turbines.
Therefore, they would not likely
consider broad geographic areas.
Nevertheless, they should consider
the presence of habitats or species of
concern before siting projects.
Development in some areas may
be precluded by federal law. This
designation is separate from a
determination through the tiered
approach that an area is not
appropriate for development due
to feasibility, ecological reasons,
or other issues. Developers are
encouraged to visit Service and
other publicly available databases

or other available information
during Tier 1 or Tier 2 to see if
a potential wind energy area is
precluded from development by
federal law. Some areas may be
protected from development through
state or local laws or ordinances,
and the appropriate agency
should be contacted accordingly.
Service field offices are available to
answer questions where they are
knowledgeable, guide developers to
databases, and refer developers to
other agency contacts.
Some areas may be inappropriate
for large scale development
because they have been recognized
according to scientifically credible
information as having high wildlife
value, based solely on their
ecological rarity and intactness (e.g.,
Audubon Important Bird Areas,
The Nature Conservancy portfolio
sites, state wildlife action plan
priority habitats). It is important
to identify such areas through the
tiered approach, as reflected in
Tier 1, Question 2 below. Many of
North America's native landscapes
are greatly diminished, with some
existing at less than 10 percent of
their pre-settlement occurrence.

2. To “screen” a landscape or set of
multiple potential sites to avoid
those with the highest habitat
values.
3. To begin to determine if a single
identified potential site poses
serious risk to species of concern
or their habitats.
Tier 1 can offer early guidance
about the sensitivity of the site
within a larger landscape context; it
can help direct development away
from sites that will be associated
with additional study need, greater
mitigation requirements, and
uncertainty; or it can identify those
sensitive resources that will need
12 

Attwater’s prairie chicken. Credit: Gary Halvorsen, USFWS

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Herbaceous scrub-shrub steppe
in the Pacific Northwest and old
growth forest in the Northeast
represent such diminished native
resources. Important remnants of
these landscapes are identified and
documented in various databases
held by private conservation
organizations, state wildlife agencies,
and, in some cases, by the Service.
Developers should collaborate with
such entities specifically about such
areas in the vicinity of a prospective
project site.

Tier 1 Questions
Questions at each tier help
determine potential environmental
risks at the landscape scale for
Tier 1 and project scale for Tiers 2
and 3. Suggested questions to be
considered for Tier 1 include:
1. Are there species of concern
present on the potential
site(s), or is habitat (including
designated critical habitat)
present for these species?
2. Does the landscape contain
areas where development is
precluded by law or areas
designated as sensitive
according to scientifically
credible information?
Examples of designated areas
include, but are not limited
to: federally-designated
critical habitat; high-priority
conservation areas for nongovernment organizations
(NGOs); or other local, state,
regional, federal, tribal, or
international categorizations.
3. Are there known critical areas
of wildlife congregation,
including, but not limited to:
maternity roosts, hibernacula,
staging areas, winter ranges,
nesting sites, migration
stopovers or corridors, leks,
or other areas of seasonal
importance?
4. Are there large areas of intact
habitat with the potential for
fragmentation, with respect to
species of habitat fragmentation

concern needing large
contiguous blocks of habitat?

Tier 1 Methods and Metrics
Developers who choose to conduct
Tier 1 investigations would generally
be able to utilize existing public or
other readily available landscapelevel maps and databases from
sources such as federal, state, or
tribal wildlife or natural heritage
programs, the academic community,
conservation organizations, or
the developers’ or consultants’
own information. The Service
recommends that developers
conduct a review of the publicly
available data. The analysis of
available sites in the region of
interest will be based on a blend
of the information available in
published and unpublished reports,
wildlife range distribution maps, and
other such sources. The developer
should check with the Service Field
Office for data specific to wind
energy development and wildlife at
the landscape scale in Tier 1.

impacts to wildlife. A developer
may consider abandoning the area
or identifying possible means by
which the project can be modified
to avoid or minimize potential
significant adverse impacts.
3. The data available in the sources
described above are insufficient
to answer one or more of the
Tier 1 questions. The developer
proceeds to Tier 2, with a specific
emphasis on collecting the data
necessary to answer the Tier 2
questions, which are inclusive of
those asked at Tier 1.

Tier 1 Decision Points
The objective of the Tier 1 process
is to help the developer identify a
site or sites to consider further for
wind energy development. Possible
outcomes of this internal screening
process include the following:
1. One or more sites are found
within the area of investigation
where the answer to each of the
above Tier 1 questions is “no,”
indicating a low probability of
significant adverse impact to
wildlife. The developer proceeds
to Tier 2 investigations and
characterization of the site
or sites, answering the Tier 2
questions with site-specific data
to confirm the validity of the
preliminary indications of low
potential for significant adverse
impact.
2. If a developer answers “yes”
to one or more of the Tier 1
questions, they should proceed
to Tier 2 to further assess the
probability of significant adverse
  13

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 3: Tier 2 – Site Characterization
At this stage, the developer has
narrowed consideration down to
specific sites, and additional data
may be necessary to systematically
and comprehensively characterize
a potential site in terms of the risk
wind energy development would
pose to species of concern and their
habitats. In the case where a site
or sites have been selected without
the Tier 1 preliminary evaluation of
the general ecological context, Tier
2 becomes the first stage in the site
selection process. The developer
will address the questions asked
in Tier 1; if addressing the Tier 1
questions here, the developer will
evaluate the site within a landscape
context. However, a distinguishing
feature of Tier 2 studies is that they
focus on site-specific information
and should include at least one visit
by a knowledgeable biologist to the
prospective site(s). Because Tier 2
studies are preliminary, normally
one reconnaissance level site visit
will be adequate as a “groundtruth” of available information.
Notwithstanding, if key issues are
identified that relate to varying
conditions and/or seasons, Tier 2
studies should include enough site
visits during the appropriate times
of the year to adequately assess
these issues for the prospective
site(s).
If the results of the site assessment
indicate that one or more species
of concern are present, a developer
should consider applicable
regulatory or other agency
processes for addressing them. For
instance, if migratory birds and bats
are likely to experience significant
adverse impacts by a wind project at
the proposed site, a developer should
identify and document possible
actions that will avoid or compensate
for those impacts. Such actions
might include, but not be limited
to, altering locations of turbines or
turbine arrays, operational changes,
or compensatory mitigation. As
soon as a developer anticipates that
14 

a wind energy project is likely to
result in a take of bald or golden
eagles, a developer should prepare
an ECP and, if necessary, apply
for a programmatic take permit.
As soon as a developer realizes
endangered or threatened species
are present and likely to be affected
by a wind project located there, a
federal agency should consult with
the Service under Section 7(a)(2) of
the ESA if the project has a federal
nexus or the developer should apply
for a section 10(a)(1)(B) incidental
take permit if there is not a federal
nexus, and incidental take of listed
wildlife is anticipated. State, tribal,
and local jurisdictions may have
additional permitting requirements.
Developers of distributed or
community scale wind projects
are typically considering limited
geographic areas to install turbines.
Therefore, they would likely be
familiar with conditions at the site
where they are considering installing
a turbine. Nevertheless, they should
do preliminary site evaluations to
determine the presence of habitats
or species of concern before siting
projects.

Open landscape with wind turbines. Credit: NREL

Tier 2 Questions
Questions suggested for Tier 2
can be answered using credible,
publicly available information that
includes published studies, technical
reports, databases, and information
from agencies, local conservation
organizations, and/or local experts.
Developers or consultants working
on their behalf should contact the
federal, state, tribal, and local
agencies that have jurisdiction
or management authority and
responsibility over the potential
project.
1. Are known species of concern
present on the proposed site, or
is habitat (including designated
critical habitat) present for
these species?
2. Does the landscape contain
areas where development is
precluded by law or designated
as sensitive according
to scientifically credible
information? Examples of
designated areas include, but
are not limited to: federallydesignated critical habitat;

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
high-priority conservation areas
for NGOs; or other local, state,
regional, federal, tribal, or
international categorizations.
3. Are there plant communities of
concern present or likely to be
present at the site(s)?
4. Are there known critical areas
of congregation of species
of concern, including, but
not limited to: maternity
roosts, hibernacula, staging
areas, winter ranges, nesting
sites, migration stopovers or
corridors, leks, or other areas of
seasonal importance?
5. Using best available scientific
information has the developer
or relevant federal, state, tribal,
and/or local agency identified
the potential presence of a
population of a species of
habitat fragmentation concern?
6. Which species of birds and bats,
especially those known to be at
risk by wind energy facilities,
are likely to use the proposed
site based on an assessment of
site attributes?
7. Is there a potential for
significant adverse impacts to
species of concern based on the
answers to the questions above,
and considering the design of
the proposed project?

Tier 2 Methods and Metrics
Obtaining answers to Tier 2
questions will involve a more
thorough review of the existing
site-specific information than in
Tier 1. Tier 2 site characterizations
studies will generally contain three
elements:
1. A review of existing information,
including existing published or
available literature and databases
and maps of topography, land
use and land cover, potential
wetlands, wildlife, habitat, and
sensitive plant distribution. If
agencies have documented
potential habitat for species of
habitat fragmentation concern,

this information can help with the
analysis.

Specific resources that can help
answer each Tier 2 question include:

2. Contact with agencies and
organizations that have relevant
scientific information to further
help identify if there are bird,
bat or other wildlife issues. The
Service recommends that the
developer make contact with
federal, state, tribal, and local
agencies that have jurisdiction or
management authority over the
project or information about the
potentially affected resources.
In addition, because key NGOs
and relevant local groups are
often valuable sources of relevant
local environmental information,
the Service recommends that
developers contact key NGOs,
even if confidentiality concerns
preclude the developer from
identifying specific project
location information at this
stage. These contacts also
provide an opportunity to identify
other potential issues and data
not already identified by the
developer.

1. Are known species of concern
present on the proposed site, or
is habitat (including designated
critical habitat) present for
these species?

3. One or more reconnaissance
level site visits by a wildlife
biologist to evaluate current
vegetation/habitat coverage
and land management/use.
Current habitat and land use
practices will be noted to help in
determining the baseline against
which potential impacts from
the project would be evaluated.
The vegetation/habitat will be
used for identifying potential
bird and bat resources occurring
at the site and the potential
presence of, or suitable habitat
for, species of concern. Vegetation
types or habitats will be noted
and evaluated against available
information such as land use/land
cover mapping. Any sensitive
resources located during the site
visit will be noted and mapped or
digital location data recorded for
future reference. Any individuals
or signs of species of concern
observed during the site visit
will be noted. If land access
agreements are not in place,
access to the site will be limited to
public roads.

Information review and agency
contact: locations of state and
federally listed, proposed and
candidate species and species
of concern are frequently
documented in state and federal
wildlife databases. Examples
include published literature such
as: Natural Heritage Databases,
State Wildlife Action Plans, NGOs
publications, and developer and
consultant information, or can
be obtained by contacting these
entities.
Site Visit: To the extent
practicable, the site visit(s) should
evaluate the suitability of habitat
at the site for species identified
and the likelihood of the project
to adversely affect the species of
concern that may be present.
2. Does the landscape contain
areas where development is
precluded by law or designated
as sensitive according
to scientifically credible
information? Examples of
designated areas include, but
are not limited to: federallydesignated critical habitat;
high-priority conservation areas
for NGOs; or other local, state,
regional, federal, tribal, or
international categorizations.
Information review and agency
contact such as: maps of political
and administrative boundaries;
National Wetland Inventory
data files; USGS National Land
Cover data maps; state, federal
and tribal agency data on areas
that have been designated to
preclude development, including
wind energy development; State
Wildlife Action Plans; State
Land and Water Resource Plans;
Natural Heritage databases;
scientifically credible information
provided by NGO and local
  15

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
4. Are there known critical areas
of wildlife congregation,
including, but not limited to,
maternity roosts, hibernacula,
staging areas, winter ranges,
nesting sites, migration
stopovers or corridors, leks,
or other areas of seasonal
importance?
Information review and agency
contact such as: existing
databases, State Wildlife Action
Plan, Natural Heritage Data, and
NGO and agency information
regarding the presence of
Important Bird Areas, migration
corridors or stopovers, leks, bat
hibernacula or maternity roosts,
or game winter ranges at the site
and in the surrounding area.
Site Visit: To the extent
practicable, the site visit should,
during appropriate times to
adequately assess these issues
for prospective site(s), evaluate
the topography, physiographic
features and uniqueness of the
site in relation to the surrounding
region to assess the potential for
the project area to concentrate
resident or migratory birds and
bats.

Tall grass prairie. Credit: Amy Thornburg, USFWS

resources; and the additional
resources listed in Appendix C:
Sources of Information Pertaining
to Methods to Assess Impacts
to Wildlife of this document, or
through contact of agencies and
NGOs, to determine the presence
of high priority habitats for
species of concern or conservation
areas.
Site Visit: To the extent
practicable, the site visit(s) should
characterize and evaluate the
uniqueness of the site vegetation
relative to surrounding areas.
3. Are plant communities of
concern present or likely to be
present at the site(s)?
16 

Information review and agency
contact such as: Natural Heritage
Data of state rankings (S1, S2, S3)
or globally (G1, G2, G3) ranked
rare plant communities.
Site Visit: To the extent
practicable, the site visit should
evaluate the topography,
physiographic features and
uniqueness of the site vegetation
in relation to the surrounding
region. If plant communities of
concern are present, developers
should also assess in Tier 3
whether the proposed project
poses risk of significant adverse
impacts and opportunities for
mitigation.

5. Using best available scientific
information, has the relevant
federal, state, tribal, and/
or local agency determined
the potential presence of a
population of a species of
habitat fragmentation concern?
If not, the developer need not
assess impacts of the proposed
project on habitat fragmentation.
Habitat fragmentation is defined
as the separation of a block
of habitat for a species into
segments, such that the genetic
or demographic viability of the
populations surviving in the
remaining habitat segments is
reduced; and risk, in this case,
is defined as the probability that
this fragmentation will occur as a
result of the project. Site clearing,
access roads, transmission lines
and turbine tower arrays remove
habitat and displace some species

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
of wildlife, and may fragment
continuous habitat areas into
smaller, isolated tracts. Habitat
fragmentation is of particular
concern when species require
large expanses of habitat for
activities such as breeding and
foraging.

A. The developer should define
the study area. The study area
should not only include the
project site for the proposed
project, but be based on the
distribution of habitat for the
local population of the species of
habitat fragmentation concern.

Consequences of isolating local
populations of some species
include decreased reproductive
success, reduced genetic diversity,
and increased susceptibility to
chance events (e.g. disease and
natural disasters), which may lead
to extirpation or local extinctions.
In addition to displacement,
development of wind energy
infrastructure may result in
additional loss of habitat for some
species due to “edge effects”
resulting from the break-up of
continuous stands of similar
vegetation resulting in an interface
(edge) between two or more types
of vegetation. The extent of edge
effects will vary by species and
may result in adverse impacts
from such effects as a greater
susceptibility to colonization by
invasive species, increased risk of
predation, and competing species
favoring landscapes with a mosaic
of vegetation.

B. The developer should analyze
the current habitat quality and
spatial configuration of the study
area for the species of habitat
fragmentation concern.

Site Visit: If the answer to Tier
2 Question 5 is yes, developers
should use the general
framework for evaluating habitat
fragmentation at a project site in
Tier 2 outlined below. Developers
and the Service may use this
method to analyze the impacts
of habitat fragmentation at wind
development project sites on
species of habitat fragmentation
concern. Service field offices may
be able to provide the available
information on habitat types,
quality and intactness. Developers
may use this information in
combination with site-specific
information on the potential
habitats to be impacted by a
potential development and how
they will be impacted.
General Framework for Evaluating
Habitat Fragmentation at a Project
Site (Tier 2)

6. Which species of birds and bats,
especially those known to be at
risk by wind energy facilities,
are likely to use the proposed
site based on an assessment of
site attributes?
Information review and agency
contact: existing published
information and databases from
NGOs and federal and state
resource agencies regarding the
potential presence of:
• Raptors: species potentially
present by season

i. Use recent aerial and remote
imagery to determine distinct
habitat patches, or boundaries,
within the study area, and
the extent of existing habitat
fragmenting features (e.g.,
highways).

• Prairie grouse and sage
grouse: species potentially
present by season and location
of known leks
• Other birds: species
potentially present by season
that may be at risk of collision
or adverse impacts to habitat,
including loss, displacement
and fragmentation

ii. Assess the level of
fragmentation of the existing
habitat for the species of
habitat fragmentation concern
and categorize into three
classes:

• Bats: species likely to be
impacted by wind energy
facilities and likely to occur on
or migrate through the site

• High quality: little or no
apparent fragmentation of
intact habitat
• Medium quality: intact
habitat exhibiting some
recent disturbance activity

Site Visit: To the extent
practicable, the site visit(s)
should identify landscape
features or habitats that could
be important to raptors, prairie
grouse, and other birds that
may be at risk of adverse
impacts, and bats, including
nesting and brood-rearing
habitats, areas of high prey
density, movement corridors
and features such as ridges
that may concentrate raptors.
Raptors, prairie grouse, and
other presence or sign of
species of concern seen during
the site visit should be noted,
with species identification if
possible.

• Low quality: Extensive
fragmentation of habitat
(e.g., row-cropped
agricultural lands, active
surface mining areas)
C. The developer should determine
potential changes in quality and
spatial configuration of the habitat
in the study area if development
were to proceed as proposed
using existing site information.
D. The developer should provide the
collective information from steps
A-C for all potential developments
to the Service for use in assessing
whether the habitat impacts,
including habitat fragmentation,
are likely to affect population
viability of the potentially affected
species of habitat fragmentation
concern.

7. Is there a potential for
significant adverse impacts to
species of concern based on the
answers to the questions above,
and considering the design of
the proposed project?

  17

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

The developer has assembled
answers to the questions above
and should make an initial
evaluation of the probability
of significant adverse impacts
to species of concern and their
habitats. The developer should
make this evaluation based on
assessments of the potential
presence of species of concern
and their habitats, potential
presence of critical congregation
areas for species of concern, and
any site visits. The developer is
encouraged to communicate the
results of these assessments with
the Service.

Tier 2 Decision Points
Possible outcomes of Tier 2 include
the following:
1. The most likely outcome of Tier 2
is that the answer to one or more
Tier 2 questions is inconclusive to
address wildlife risk, either due
to insufficient data to answer the
question or because of uncertainty
about what the answers indicate.
The developer proceeds to Tier 3,
formulating questions, methods,
and assessment of potential
mitigation measures based on
issues raised in Tier 2 results.
2. Sufficient information is
available to answer all Tier 2
questions, and the answer to
each Tier 2 question indicates
a low probability of significant
adverse impact to wildlife (for
example, infill or expansion of an
existing facility where impacts
have been low and Tier 2 results
indicate that conditions are
similar, therefore wildlife risk is
low). The developer may then
decide to proceed to obtain state
and local permit (if required),
design, and construction following
best management practices (see
Chapter 7: Best Management
Practices).
3. Sufficient information is available
to answer all Tier 2 questions, and
the answer to each Tier 2 question
indicates a moderate probability
of significant adverse impacts
to species of concern or their
18 

habitats. The developer should
proceed to Tier 3 and identify
measures to mitigate potential
significant adverse impacts to
species of concern.
4. The answers to one or more
Tier 2 questions indicate a high
probability of significant adverse
impacts to species of concern or
their habitats that:
a) Cannot be adequately
mitigated. The proposed site
should be abandoned.
b) Can be adequately mitigated.
The developer should
proceed to Tier 3 and identify
measures to mitigate potential
significant adverse impacts
to species of concern or their
habitats.

Greater sage grouse, Credit: Stephen Ting, USFWS

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 4: Tier 3 – Field Studies to Document Site
Wildlife and Habitat and Predict Project Impacts
Tier 3 is the first tier in which
a developer would conduct
quantitative and scientifically
rigorous studies to assess the
potential risk of the proposed
project. Specifically, these studies
provide pre-construction information
to:
• Further evaluate a site for
determining whether the
wind energy project should be
developed or abandoned
• Design and operate a site to avoid
or minimize significant adverse
impacts if a decision is made to
develop
• Design compensatory mitigation
measures if significant adverse
habitat impacts cannot acceptably
be avoided or minimized
• Determine duration and level
of effort of post-construction
monitoring. If warranted,
provide the pre-construction
component of post-construction
studies necessary to estimate and
evaluate impacts

At the beginning of Tier 3, a
developer should communicate
with the Service on the preconstruction studies. At the
end of Tier 3, developers should
communicate with the Service
regarding the results of the Tier 3
studies and consider the Service’s
comments and recommendations
prior to completing the Tier 3
decision process. The Service will
provide written comments to a
developer that identify concerns
and recommendations to resolve the
concerns based on study results and
project development plans.
Not all Tier 3 studies will continue
into Tiers 4 or 5. For example,
surveys conducted in Tier 3 for
species of concern may indicate one
or more species are not present at
the proposed project site, or siting
decisions could be made in Tier 3
that remove identified concerns, thus
removing the need for continued
efforts in later tiers. Additional
detail on the design issues for postconstruction studies that begin in
Tier 3 is provided in the discussion of
methods and metrics in Tier 3.

Turkey vulture and wind turbine. Credit: Rachel London, USFWS

Tier 3 Questions
Tier 3 begins as the other tiers,
with problem formulation: what
additional studies are necessary to
enable a decision as to whether the
proposed project can proceed to
construction or operation or should
be abandoned? This step includes
an evaluation of data gaps identified
by Tier 2 studies as well as the
gathering of data necessary to:
• Design a project to avoid or
minimize predicted risk
• Evaluate predictions of
impact and risk through postconstruction comparisons of
estimated impacts
• Identify compensatory mitigation
measures, if appropriate, to offset
significant adverse impacts that
cannot be avoided or minimized
The problem formulation stage
for Tier 3 also will include an
assessment of which species
identified in Tier 1 and/or Tier 2 will
be studied further in the site risk
assessment. This determination is
based on analysis of existing data
from Tier 1 and existing site-specific
data and Project Site (see Glossary
in Appendix A) visit(s) in Tier 2, and
on the likelihood of presence and the
degree of adverse impact to species
or their habitat. If the habitat is
suitable for a species needing further
study and the site occurs within
the historical range of the species,
or is near the existing range of the
species but presence has not been
documented, additional field studies
may be appropriate. Additional
analyses should not be necessary if
a species is unlikely to be present
or is present but adverse impact is
unlikely or of minor significance.
Tier 3 studies address many of
the questions identified for Tiers
1 and 2, but Tier 3 studies differ
because they attempt to quantify
  19

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
the distribution, relative abundance,
behavior, and site use of species of
concern. Tier 3 data also attempt
to estimate the extent that these
factors expose these species to risk
from the proposed wind energy
facility. Therefore, in answering Tier
3 questions 1-3, developers should
collect data sufficient to analyze and
answer Tier 3 questions 4-6. High
risk sites may warrant additional
years of pre-construction studies.
The duration and intensity of studies
needed should be determined
through communication with the
Service.
If Tier 3 studies identify species
of concern or important habitats,
e.g., wetlands, which have
specific regulatory processes and
requirements, developers should
work with appropriate state,
tribal, or federal agencies to obtain
required authorizations or permits.
Tier 3 studies should be designed to
answer the following questions:
1. Do field studies indicate that
species of concern are present
on or likely to use the proposed
site?
2. Do field studies indicate
the potential for significant
adverse impacts on affected
population of species of habitat
fragmentation concern?
3. What is the distribution,
relative abundance, behavior,
and site use of species of
concern identified in Tiers 1 or
2, and to what extent do these
factors expose these species to
risk from the proposed wind
energy project?
4. What are the potential risks
of adverse impacts of the
proposed wind energy project
to individuals and local
populations of species of
concern and their habitats? (In
the case of rare or endangered
species, what are the possible
impacts to such species and
their habitats?)

20 

5. How can developers mitigate
identified significant adverse
impacts?
6. Are there studies that should
be initiated at this stage that
would be continued in postconstruction?
The Service encourages the use of
common methods and metrics in
Tier 3 assessments for measuring
wildlife activity and habitat features.
Common methods and metrics
provide great benefit over the
long-term, allowing for comparisons
among projects and for greater
certainty regarding what will be
asked of the developer for a specific
project. Deviation from commonly
used methods should be carefully
considered, scientifically justifiable
and discussed with federal, tribal,
or state natural resource agencies,
or other credible experts, as
appropriate. It may be useful to
consult other scientifically credible
information sources.
Tier 3 studies will be designed to
accommodate local and regional
characteristics. The specific
protocols by which common methods
and metrics are implemented in Tier
3 studies depend on the question
being addressed, the species or
ecological communities being studied
and the characteristics of the study
sites. Federally-listed threatened
and endangered species, eagles, and
some other species of concern and
their habitats, may have specific
protocols required by local, state
or federal agencies. The need for
special surveys and mapping that
address these species and situations
should be discussed with the
appropriate stakeholders.
In some instances, a single method
will not adequately assess potential
collision risk or habitat impact. For
example, when there is concern
about moderate or high risk to
nocturnally active species, such as
migrating passerines and local and
migrating bats, a combination of
remote sensing tools such as radar,
and acoustic monitoring for bats
and indirect inference from diurnal

bird surveys during the migration
period may be necessary. Answering
questions about habitat use by
songbirds may be accomplished by
relatively small-scale observational
studies, while answering the same
question related to wide-ranging
species such as prairie grouse and
sage grouse may require more
time-consuming surveys, perhaps
including telemetry.
Because of the points raised above
and the need for flexibility in
application, the Guidelines do not
make specific recommendations
on protocol elements for Tier 3
studies. The peer-reviewed scientific
literature (such as the articles cited
throughout this section) contains
numerous recently published
reviews of methods for assessing
bird and bat activity, and tools for
assessing habitat and landscape level
risk. Details on specific methods and
protocols for recommended studies
are or will be widely available and
should be consulted by industry and
agency professionals.
Many methods for assessing
risk are components of active
research involving collaborative
efforts of public-private research
partnerships with federal, state
and tribal agencies, wind energy
developers and NGOs interested in
wind energy-wildlife interactions
(e.g., Bats and Wind Energy
Cooperative and the Grassland
Shrub Steppe Species Cooperative).
It is important to recognize the need
to integrate the results of research
that improves existing methods
or describes new methodological
developments, while acknowledging
the value of utilizing common
methods that are currently available.
The methods and metrics that
may be appropriate for gathering
data to answer Tier 3 questions
are compiled and outlined in the
Technical Resources section, page
26. These are not meant to be
all inclusive and other methods
and metrics are available, such as
the NWCC Methods & Metrics
document (Strickland et al. 2011)
and others listed in Appendix C:

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
State, federal and tribal agencies
often require specific protocols be
followed when species of concern
are potentially present on a site.
The methods and protocols for
determining presence of species
of concern at a site are normally
established for each species and
required by federal, state and
tribal resource agencies. Surveys
should sample the wind turbine
sites and applicable disturbance
area during seasons when species
are most likely present. Normally,
the methods and protocols by which
they are applied also will include an
estimate of relative abundance. Most
presence/absence surveys should
be done following a probabilistic
sampling protocol to allow statistical
extrapolation to the area and time of
interest.
Avian Radar

Sources of Information Pertaining
to Methods to Assess Impacts to
Wildlife.
Each question should be considered
in turn, followed by a discussion of
the methods and their applicability.
1. Do field studies indicate that
species of concern are present
on or likely to use the proposed
site?
In many situations, this question can
be answered based on information
accumulated in Tier 2. Specific
presence/absence studies may not be
necessary, and protocol development
should focus on answering the
remaining Tier 3 questions.
Nevertheless, it may be necessary
to conduct field studies to determine
the presence, or likelihood of
presence, when little information is
available for a particular site. The
level of effort normally contemplated
for Tier 3 studies should detect
common species and species that are
relatively rare, but which visit a site
regularly (e.g., every year). In the
event a species of concern is very
rare and only occasionally visits a
site, a determination of “likely to
occur” would be inferred from the
habitat at the site and historical
records of occurrence on or near the
site.

Determining the presence of
diurnally or nocturnally active
mammals, reptiles, amphibians,
and other species of concern
will typically be accomplished
by following agency-required
protocols. Most listed species have
required protocols for detection
(e.g., the black-footed ferret).
State, tribal and federal agencies
should be contacted regarding
survey protocols for those species of
concern. See Corn and Bury 1990,
Olson et al. 1997, Bailey et al. 2004,
Graeter et al. 2008 for examples of
reptile and amphibian protocols,
survey and analytical methods. See
Tier 3 Study Design Considerations
on page 24 for further details.
2. Do field studies indicate the
potential for significant adverse
impacts on affected populations
of species of habitat
fragmentation concern?
If Tier 2 studies indicate the
presence of species of habitat
fragmentation concern, but existing
information did not allow for a
complete analysis of potential
impacts and decision-making, then
additional studies and analyses
should take place in Tier 3.
As in Tier 2, the particulars of the
analysis will depend on the species
of habitat fragmentation concern
and how habitat block size and

fragmentation are defined for the life
cycles of that species, the likelihood
that the project will adversely affect
a local population of the species and
the significance of these impacts to
the viability of that population.
To assess habitat fragmentation
in the project vicinity, developers
should evaluate landscape
characteristics of the proposed site
prior to construction and determine
the degree to which habitat for
species of habitat fragmentation
concern will be significantly altered
by the presence of a wind energy
facility.
A general framework for evaluating
habitat fragmentation at a project
site, following that described in
Tier 2, is outlined on page 27. This
framework should be used in those
circumstances when the developer,
or a relevant federal, state,
tribal and/or other local agency
determines the potential presence of
a population of a species of habitat
fragmentation concern that may be
adversely affected by the project.
Otherwise, the developer need not
assess the impacts of the proposed
project on habitat fragmentation.
This method for analysis of habitat
fragmentation at project sites must
be adapted to the local population of
the species of habitat fragmentation
concern potentially affected by the
proposed development.
3. What is the distribution,
relative abundance, behavior,
and site use of species of
concern identified in Tiers 1 or
2, and to what extent do these
factors expose these species to
risk from the proposed wind
energy project?
For those species of concern that
are considered at risk of collisions or
habitat impacts, the questions to be
answered in Tier 3 include: where
are they likely to occur (i.e., where
is their habitat) within a project
site or vicinity, when might they
occur, and in what abundance. The
spatial distribution of species at
risk of collision can influence how a
site is developed. This distribution
should include the airspace for flying
species with respect to the rotor  21

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
swept zone. The abundance of a
species and the spatial distribution of
its habitat can be used to determine
the relative risk of impact to species
using the sites, and the absolute risk
when compared to existing projects
where similar information exists.
Species abundance and habitat
distribution can also be used in
modeling risk factors.
Surveys for spatial distribution

birds, bats, and other wildlife are
found in the Technical Resources
section on page 26.
4. What are the potential risks
of adverse impacts of the
proposed wind energy project
to individuals and local
populations of species of
concern and their habitats? (In
the case of rare or endangered
species, what are the possible

Whooping crane. Credit: Ryan Hagerty, USFWS

and relative abundance require
coverage of the wind turbine sites
and applicable site disturbance
area, or a sample of the area
using observational methods for
the species of concern during
the seasons of interest. As with
presence/absence (see Tier 3,
question 1, above) the methods
used to determine distribution,
abundance, and behavior may vary
with the species and its ecology.
Spatial distribution is determined by
applying presence/absence or using
surveys in a probabilistic manner
over the entire area of interest.
Suggested survey protocols for
22 

impacts to such species and
their habitats?)
Methods used for estimating
risk will vary with the species of
concern. For example, estimating
potential bird fatalities in Tier 3
may be accomplished by comparing
exposure estimates (described
earlier in estimates of bird use) at
the proposed site with exposure
estimates and fatalities at existing
projects with similar characteristics
(e.g., similar technology, landscape,
and weather conditions). If models
are used, they may provide an
additional tool for estimating

fatalities, and have been used in
Australia (Organ and Meredith
2004), Europe (Chamberlin et
al. 2006), and the United States
(Madders and Whitfield 2006). As
with other prediction tools, model
predictions should be evaluated and
compared with post-construction
fatality data to validate the
models. Models should be used as a
subcomponent of a risk assessment
based on the best available empirical
data. A statistical model based on
the relationship of pre-construction
estimates of raptor abundance and
post-construction raptor fatalities is
described in Strickland et al. (2011)
and promises to be a useful tool for
risk assessment.
Collision risk to individual birds
and bats at a particular wind
energy facility may be the result of
complex interactions among species
distribution, relative abundance,
behavior, weather conditions
(e.g., wind, temperature) and site
characteristics. Collision risk for an
individual may be low regardless of
abundance if its behavior does not
place it within the rotor-swept zone.
If individuals frequently occupy the
rotor-swept zone but effectively
avoid collisions, they are also at
low risk of collision with a turbine
(e.g., ravens). Alternatively, if the
behavior of individuals frequently
places them in the rotor-swept
zone, and they do not actively avoid
turbine blade strikes, they are at
higher risk of collisions with turbines
regardless of abundance. For a
given species (e.g., red-tailed hawk),
increased abundance increases
the likelihood that individuals
will be killed by turbine strikes,
although the risk to individuals
will remain about the same. The
risk to a population increases as
the proportion of individuals in
the population at risk to collision
increases.
At some projects, bat fatalities
are higher than bird fatalities, but
the exposure risk of bats at these
facilities is not fully understood
(National Research Council (NRC)
2007). Horn et al. (2008) and Cryan
(2008) hypothesize that bats are
attracted to turbines, which, if true,
would further complicate estimation

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
of exposure. Further research is
required to determine if bats are
attracted to turbines and if so, to
evaluate 1) the influence on Tier
2 methods and predictions, and
2) if this increased individual risk
translates into higher populationlevel impacts for bats.
The estimation of indirect impact
risk requires an understanding
of animal behavior in response to
a project and its infrastructure,
and a pre-construction estimate of
presence/absence of species whose
behavior would cause them to avoid
areas in proximity to turbines, roads
and other components of the project.
The amount of habitat that is lost to
indirect impacts will be a function
of the sensitivity of individuals
to the project and to the activity
levels associated with the project’s
operations. The population-level
significance of this indirect impact
will depend on the amount of habitat
available to the affected population.
If the indirect impacts include
habitat fragmentation, then the
risk to the demographic and genetic
viability of the isolated animals is
increased. Quantifying cause and
effect may be very difficult, however.
5. How can developers mitigate
identified significant adverse
impacts?
Results of Tier 3 studies should
provide a basis for identifying
measures to mitigate significant
adverse impacts predicted for
species of concern. Information on
wildlife use of the proposed area is
most useful when designing a project
to avoid or minimize significant
adverse impacts. In cases of
uncertainty with regard to impacts
to species of concern, additional
studies may be necessary to quantify
significant adverse impacts and
determine the need for mitigation of
those impacts.
Chapter 7, Best Management
Practices, and Chapter 8, Mitigation,
outline measures that can be taken

5

to mitigate impacts throughout all
phases of a project.
The following discussion of prairie
grouse and sage grouse as species of
concern illustrates the uncertainty
mentioned above by describing
the present state of scientific
knowledge relative to these species,
which should be considered when
designing mitigation measures. The
extent of the impact of wind energy
development on prairie grouse and
sage grouse lekking activity (e.g.,
social structure, mating success,
persistence) and the associated
impacts on productivity (e.g.,
nesting, nest success, chick survival)
is poorly understood (Arnett et al.
2007, NRC 2007, Manville 2004).
However, recent published research
documents that anthropogenic
features (e.g., tall structures,
buildings, roads, transmission lines)
can adversely impact vital rates
(e.g., nesting, nest success, lekking
behavior) of lesser prairie-chickens
(Pruett et al. 2009, Pitman et al.
2005, Hagen et al. 2009, Hagen et al.
2011) and greater prairie-chickens
over long distances. Pitman et
al. (2005) found that transmission
lines reduced nesting of lesser
prairie chicken by 90 percent out to
a distance of 0.25 miles, improved
roads at a distance of 0.25 miles, a
house at 0.3 miles, and a power plant
at >0.6 miles. Reduced nesting
activity of lesser prairie chickens
may extend farther, but Pitman
et al. (2005) did not analyze their
data for lower impacts (less than
90 percent reduction in nesting)
of those anthropogenic features
on lesser prairie chicken nesting
activities at greater distances.
Hagen et al. (2011) suggested that
development within 1 to 1 ½ miles
of active leks of prairie grouse may
have significant adverse impacts on
the affected grouse population. It
is not unreasonable to infer that
impacts from wind energy facilities
may be similar to those from these
other anthropogenic structures.
Kansas State University, as part
of the National Wind Coordinating

Collaborative’s Grassland and
Shrub Steppe Species Subgroup, is
undertaking a multi-year telemetry
study to evaluate the effects of a
proposed wind-energy facility on
displacement and demographic
parameters (e.g., survival, nest
success, brood success, fecundity) of
greater prairie-chickens in Kansas.5
The distances over which
anthropogenic activities impact
sage grouse are greater than for
prairie grouse. Based primarily
on data documenting reduced
fecundity (a combination of nesting,
clutch size, nest success, juvenile
survival, and other factors) in
sage grouse populations near
roads, transmissions lines, and
areas of oil and gas development/
production (Holloran 2005, Connelly
et al. 2000), development within
three to five miles (or more) of
active sage grouse leks may have
significant adverse impacts on the
affected grouse population. Lyon
and Anderson (2003) found that in
habitats fragmented by natural gas
development, only 26 percent of hens
captured on disturbed leks nested
within 1.8 miles of the lek of capture,
whereas 91 percent of hens from
undisturbed areas nested within the
same area. Holloran (2005) found
that active drilling within 3.1 miles of
sage grouse lek reduced the number
of breeding males by displacing adult
males and reducing recruitment of
juvenile males. The magnitudes and
proximal causes (e.g., noise, height
of structures, movement, human
activity, etc.) of those impacts on vital
rates in grouse populations are areas
of much needed research (Becker
et al. 2009). Data accumulated
through such research may improve
our understanding of the buffer
distances necessary to avoid or
minimize significant adverse impacts
to prairie grouse and sage grouse
populations.
When significant adverse impacts
cannot be fully avoided or
adequately minimized, some form
of compensatory mitigation may be

www.nationalwind.org

  23

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
appropriate to address the loss of
habitat value. For example, it may
be possible to mitigate habitat loss or
degradation for a species of concern
by enhancing or restoring nearby
habitat value comparable to that
potentially influenced by the project.
6. Are there studies that should
be initiated at this stage that
would be continued in postconstruction?
During Tier 3 problem formulation,
it is necessary to identify the
studies needed to address the
Tier 3 questions. Consideration
of how the resulting data may be
used in conjunction with postconstruction Tier 4 and 5 studies
is also recommended. The design
of post-construction impact or
mitigation assessment studies
will depend on the specific impact
questions being addressed. Tier 3
predictions will be evaluated using
data from Tier 4 studies designed
to estimate fatalities for species
of concern and impacts to their
habitat, including species of habitat
fragmentation concern. Tier 3
studies may demonstrate the need
for mitigation of significant adverse
impacts. Where Tier 3 studies
indicate the potential for significant
adverse direct and indirect impacts
to habitat, Tier 4 studies will provide
data that evaluate predictions of
those impacts, and Tier 5 studies,
if necessary, will provide data to
evaluate the effect of those impacts
on populations and the effectiveness
of mitigation measures. Evaluations
of the impacts of a project on
demographic parameters of local
populations, habitat use, or some
other parameter(s) are considered
Tier 5 studies, and typically will
require data on these parameters
prior to as well as after construction
of the project.

Tier 3 Study Design Considerations
Specific study designs will vary from
site to site and should be adjusted
to the circumstances of individual
projects. Study designs will depend
on the types of questions, the specific
project, and practical considerations.
The most common considerations
24 

Rows of wind turbines. Credit: Joshua Winchell, USFWS

include the area being studied, the
species of concern and potential
risk to those species, potentially
confounding variables, time available
to conduct studies, project budget,
and the magnitude of the anticipated
impacts. Studies will be necessary
in part to assess a) which species
of concern are present within the
project area; b) how these species
are using the area (behavior); and c)
what risks are posed to them by the
proposed wind energy project.
Assessing Presence
A developer should assess whether
species of concern are likely to be
present in the project area during
the life of the project. Assessing
species use from databases and site
characteristics is a potential first
step. However, it can be difficult
to assess potential use by certain
species from site characteristics
alone. Various species in different
locations may require developers
to use specific survey protocols or
make certain assumptions regarding
presence. Project developers should
seek local wildlife expertise, such as
Service Field Office staff, in using
the proper procedures and making
assumptions.
Some species will present particular

challenges when trying to determine
potential presence. For instance,
species that a) are rare or cryptic;
b) migrate, conduct other daily
movements, or use areas for short
periods; c) are small or nocturnal; or
d) have become extirpated in parts of
their historical range can be difficult
to observe. One of these challenges
is migration, broadly defined as the
act of moving from one spatial unit
to another (Baker 1978), or as a
periodic movement of animals from
one location to another. Migration
is species-specific, and for birds and
bats occurs throughout the year.
Assessing Site Use/Behavior
Developers should monitor potential
sites to determine the types of
migratory species present, what
type of spatial and temporal use
these species make of the site (e.g.,
chronology of migration or other
use), and the ecological function
the site may provide in terms of the
migration cycle of these species.
Wind developers should determine
not only what species may migrate
through a proposed development site
and when, but also whether a site
may function as a staging area or
stopover habitat for wildlife on their
migration pathway.

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
For some species, movements
between foraging and breeding
habitat, or between sheltering
and feeding habitats, occur on a
daily basis. Consideration of daily
movements (morning and evening;
coming and going) is a critical
factor when considering project
development.
Duration/Intensity of Studies
Where pre-construction assessments
are warranted to help assess risk
to wildlife, the studies should be of
sufficient duration and intensity to
ensure adequate data are collected
to accurately characterize wildlife
presence and use of the area. In
ecological systems, resource
quality and quantity can fluctuate
rapidly. These fluctuations occur
naturally, but human actions can
significantly affect (i.e., increase
or decrease) natural oscillations.
Pre-construction monitoring and
assessment of proposed wind
energy sites are “snapshots in
time,” showing occurrence or no
occurrence of a species or habitat at
the specific time surveyed. Often
due to prohibitive costs, assessments
and surveys are conducted for very
low percentages (e.g., less than 5
percent) of the available sample time
in a given year, however, these data
are used to support risk analyses
over the projected life of a project
(e.g., 30 years of operations).
To establish a trend in site use
and conditions that incorporates
annual and seasonal variation in
meteorological conditions, biological
factors, and other variables, preconstruction studies may need to
occur over multiple years. However,
the level of risk and the question of
data requirements will be based on
site sensitivity, affected species, and
the availability of data from other
sources. Accordingly, decisions
regarding studies should consider
information gathered during the
previous tiers, variability within and
between seasons, and years where
variability is likely to substantially
affect answers to the Tier 3
questions. These studies should
also be designed to collect data
during relevant breeding, feeding,
sheltering, staging, or migration

periods for each species being
studied. Additionally, consideration
for the frequency and intensity of
pre-construction monitoring should
be site-specific and determined
through consultation with an expert
authority based on their knowledge
of the specific species, level of risk
and other variables present at each
individual site.
Assessing Risk to Species of
Concern
Once likely presence and factors
such as abundance, frequency of use,
habitat use patterns, and behavior
have been determined or assumed,
the developer should consider and/or
determine the consequences to the
“populations” and species.
Below is a brief discussion of several
types of risk factors that can be
considered. This does not include all
potential risk factors for all species,
but addresses the most common
ones.
Collision
Collision likelihood for individual
birds and bats at a particular wind
energy facility may be the result of
complex interactions among species
distribution, “relative abundance,"
behavior, visibility, weather
conditions, and site characteristics.
Collision likelihood for an individual
may be low regardless of abundance
if its behavior does not place it within
the “rotor-swept zone.” Individuals
that frequently occupy the rotorswept zone but effectively avoid
collisions are also at low likelihood of
collision with a turbine.

the exposure risk of bats at these
facilities is not fully understood.
Researchers (Horn et al. 2008
and Cryan 2008) hypothesize
that some bats may be attracted
to turbines, which, if true, would
further complicate estimation of
exposure. Further research is
required to determine whether
bats are attracted to turbines
and if so, whether this increased
individual risk translates into higher
population-scale effects.
Habitat Loss and Degradation
Wind project development results
in direct habitat loss and habitat
modification, especially at sites
previously undeveloped. Many of
North America's native landscapes
are greatly diminished or degraded
from multiple causes unrelated to
wind energy. Important remnants of
these landscapes are identified and
documented in various databases
held by private conservation
organizations, state wildlife
agencies, and, in some cases, by the
Service. Species that depend on
these landscapes are susceptible to
further loss of habitat, which will
affect their ability to reproduce and
survive. While habitat lost due to
footprints of turbines, roads, and
other infrastructure is obvious, less
obvious is the potential reduction of
habitat quality.
Habitat Fragmentation

Alternatively, if the behavior of
individuals frequently places them
in the rotor-swept zone, and they
do not actively avoid turbine blade
strikes, they are at higher likelihood
of collisions with turbines regardless
of abundance. Some species, even at
lower abundance, may have a higher
collision rate than similar species
due to subtle differences in their
ecology and behavior.

Habitat fragmentation separates
blocks of habitat for some species
into segments, such that the
individuals in the remaining
habitat segments may suffer from
effects such as decreased survival,
reproduction, distribution, or use of
the area. Site clearing, access roads,
transmission lines, and arrays of
turbine towers may displace some
species or fragment continuous
habitat areas into smaller, isolated
tracts. Habitat fragmentation is
of particular concern when species
require large expanses of habitat for
activities such as breeding, foraging,
and sheltering.

At many projects, the numbers
of bat fatalities are higher than
the numbers of bird fatalities, but

Habitat fragmentation can result
in increases in “edge” resulting
in direct effects of barriers
  25

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
and displacement as well as
indirect effects of nest parasitism
and predation. Sensitivity to
fragmentation effects varies among
species. Habitat fragmentation
and site modification are important
issues that should be assessed at
the landscape scale early in the
siting process. Identify areas of
high sensitivity due to the presence
of blocks of native habitats, paying
particular attention to known or
suspected “species sensitive to
habitat fragmentation.”
Displacement and Behavioral
Changes
Estimating displacement risk
requires an understanding of
animal behavior in response to a
project and its infrastructure and
activities, and a pre-construction
estimate of presence/absence of
species whose behavior would
cause them to avoid or seek areas
in proximity to turbines, roads, and
other components of the project.
Displacement is a function of the
sensitivity of individuals to the
project and activity levels associated
with operations.

post-construction data in the areas
of interest and reference areas is
possible, then the Before-AfterControl-Impact (BACI) is the most
statistically robust design. The
BACI design is most like the classic
manipulative experiment.6 In the
absence of a suitable reference area,
the design is reduced to a BeforeAfter (BA) analysis of effect where
the differences between pre- and
post-construction parameters of
interest are assumed to be the
result of the project, independent of
other potential factors affecting the
assessment area. With respect to BA
studies, the key question is whether
the observations taken immediately
after the incident can reasonably
be expected within the expected
range for the system (Manly 2009).
Reliable quantification of impact
usually will include additional study

Indirect Effects
Wind development can also have
indirect effects to wildlife and
habitats. Indirect effects include
reduced nesting and breeding
densities and the social ramifications
of those reductions; loss or
modification of foraging habitat;
loss of population vigor and overall
population density; increased
isolation between habitat patches,
loss of habitat refugia; attraction
to modified habitats; effects on
behavior, physiological disturbance,
and habitat unsuitability. Indirect
effects can result from introduction
of invasive plants; increased
predator populations or facilitated
predation; alterations in the natural
fire regime; or other effects, and can
manifest themselves later in time
than the causing action.
When collection of both pre- and
6

Virginia big-eared bat. Credit: USFWS

components to limit variation and
the confounding effects of natural
factors that may change with time.
The developer’s timeline for the
development of a wind energy
facility often does not allow
for the collection of sufficient

pre-construction data and/or
identification of suitable reference
areas to complete a BACI or BA
study. Furthermore, alterations in
land use or disturbance over the
course of a multi-year BACI or BA
study may complicate the analysis of
study results. Additional discussion
of these issues can be found in Tier 5
Study Design Considerations.

Tier 3 Technical Resources
The following methods and metrics
are provided as suggested sources
for developers to use in answering
the Tier 3 questions.
Tier 3, Question 1
Acoustic monitoring can be a
practical method for determining the
presence of threatened, endangered
or otherwise rare species of bats
throughout a proposed project (Kunz
et al. 2007). There are two general
types of acoustic detectors used
for collection of information on bat
activity and species identification:
the full-spectrum, time-expansion
and the zero-crossing techniques for
ultrasound bat detection (see Kunz
et al. 2007 for detailed discussion).
Full-spectrum time expansion
detectors provide nearly complete
species discrimination, while zerocrossing detectors provide reliable
and cost-effective estimates of
total bat use at a site and some
species discrimination. Myotis
species can be especially difficult
to discriminate with zero-crossing
detectors (Kunz et al. 2007). Kunz et
al. (2007) describe the strengths and
weaknesses of each technique for
ultrasonic bat detection, and either
type of detector may be useful in
most situations except where species
identification is especially important
and zero-crossing methods are
inadequate to provide the necessary
data. Bat acoustics technology is
evolving rapidly and study objectives
are an important consideration when
selecting detectors. When rare
or endangered species of bats are
suspected, sampling should occur
during different seasons and at

In this context, such designs are not true experiments in that the treatments (project development and control) are not randomly assigned to an
experimental unit, and there is often no true replication. Such constraints are not fatal flaws, but do limit statistical inferences of the results.

26 

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
multiple sampling stations to account
for temporal and spatial variability.
Mist-netting for bats is required in
some situations by state agencies,
Tribes, and the Service to determine
the presence of threatened,
endangered or otherwise rare
species. Mist-netting is best
used in combination with acoustic
monitoring to inventory the species
of bats present at a site, especially to
detect the presence of threatened or
endangered species. Efforts should
concentrate on potential commuting,
foraging, drinking, and roosting
sites (Kuenzi and Morrison 1998,
O'Farrell et al. 1999). Mist-netting
and other activities that involve
capturing and handling threatened
or endangered species of bats will
require permits from state and/or
federal agencies.
Tier 3, Question 2
The following protocol should be
used to answer Tier 3, Question 2.
This protocol for analysis of habitat
fragmentation at project sites should
be adapted to the species of habitat
fragmentation concern as identified
in response to Question 5 in Tier
2 and to the landscape in which
development is contemplated. The
developer should:
1. Define the study area. The study
area for the site should include
the “footprint” for the proposed
facility plus an appropriate
surrounding area. The extent
of the study area should be
based on the area where there is
potential for significant adverse
habitat impacts, including indirect
impacts, within the distribution of
habitat for the species of habitat
fragmentation concern.
2. Determine the potential for
occupancy of the study area based
on the guidance provided for the
species of habitat fragmentation
concern described above in
Question 1.
3. Analyze current habitat quality
and spatial configuration of the
study area for the species of
habitat fragmentation concern.

a. Use recent aerial or remote
imagery to determine distinct
habitat patches or boundaries
within the study area, and
the extent of existing habitat
fragmenting features.
i. Assess the level of
fragmentation of the
existing habitat for
the species of habitat
fragmentation concern and
categorize into three classes:
• High quality: little or no
apparent fragmentation
of intact habitat
• Medium quality: intact
habitat exhibiting some
recent disturbance
activity
• Low quality: extensive
fragmentation of habitat
(e.g., row-cropped
agricultural lands, active
surface mining areas)
ii. Determine edge and
interior habitat metrics of
the study area:
• Identify habitat, nonhabitat landscape
features and existing
fragmenting features
relative to the species of
habitat fragmentation
concern, to estimate
existing edge
• Calculate area and acres
of edge
• Calculate area of intact
patches of habitat
and compare to needs
of species of habitat
fragmentation concern
b. Determine potential changes in
quality and spatial configuration
of the habitat in the study
area if development proceeds
as proposed using existing
site information and the best
available spatial data regarding
placement of wind turbines and
ancillary infrastructure:

i. Identify, delineate and
classify all additional
features added by the
development that potentially
fragment habitat for
the species of habitat
fragmentation concern (e.g.,
roads, transmission lines,
maintenance structures, etc.)
ii. Assess the expected future
size and quality of habitat
patches for the species
of habitat fragmentation
concern and the additional
fragmenting features, and
categorize into three classes
as described above
iii. Determine expected future
acreages of edge and interior
habitats
iv. Calculate the area of the
remaining patches of intact
habitat
c. Compare pre-construction and
expected post-construction
fragmentation metrics:
i. Determine the area of
intact habitat lost (to the
displacement footprint or by
alteration due to the edge
effect)
ii. Identify habitat patches that
are expected to be moved
to a lower habitat quality
classification as a result of
the development
4. Assess the likelihood of a
significant reduction in the
demographic and genetic viability
of the local population of the
species of habitat fragmentation
concern using the habitat
fragmentation information
collected under item 3 above
and any currently available
demographic and genetic data.
Based on this assessment, the
developer makes the finding
whether or not there is significant
reduction. The developer should
share the finding with the relevant
agencies. If the developer finds
the likelihood of a significant
reduction, the developer should
  27

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
consider items a, b or c below:
a. Consider alternative
locations and development
configurations to minimize
fragmentation of habitat in
communication with species
experts, for all species of
habitat fragmentation concern
in the area of interest.
b. Identify high quality habitat
parcels that may be protected
as part of a plan to limit future
loss of habitat for the impacted
population of the species of
habitat fragmentation concern
in the area.
c. Identify areas of medium or
low quality habitat within
the range of the impacted
population that may be
restored or improved to
compensate for losses of
habitat that result from the
project (e.g., management of
unpaved roads and ORV trails).

levels of activity within the rotorswept zone.
Avian point counts should follow
the general methodology described
by Reynolds et al. (1980) for point
counts within a fixed area, or the line
transect survey similar to Schaffer
and Johnson (2008), where all birds
seen within a fixed distance of a
line are counted. These methods
are most useful for pre- and postconstruction studies to quantify
avian use of the project site by
habitat, determine the presence of
species of concern, and to provide a
baseline for assessing displacement
effects and habitat loss. Point
counts for large birds (e.g., raptors)
follow the same point count method
described by Reynolds et al. (1980),
Ralph et al. (1993) and Ralph et al.
1995).
Point count plots, transects, and
observational studies should allow

Tier 3, Question 3
The following protocols are
suggested for use in answering Tier
3, Question 3.
Bird distribution, abundance,
behavior and site use
Diurnal Avian Activity Surveys
The commonly used data collection
methods for estimating the spatial
distribution and relative abundance
of diurnal birds includes counts
of birds seen or heard at specific
survey points (point count), along
transects (transect surveys), and
observational studies. Both methods
result in estimates of bird use,
which are assumed to be indices of
abundance in the area surveyed.
Absolute abundance is difficult
to determine for most species
and is not necessary to evaluate
species risk. Depending on the
characteristics of the area of interest
and the bird species potentially
affected by the project, additional
pre-construction study methods may
be necessary. Point counts or line
transects should collect vertical as
well as horizontal data to identify
28 

Hoary bat. Credit: Paul Cryan, USGS

for statistical extrapolation of data
and be distributed throughout the
area of interest using a probability
sampling approach (e.g., systematic
sample with a random start). For
most projects, the area of interest
is the area where wind turbines and
permanent meteorological (met)
towers are proposed or expected to
be sited. Alternatively, the centers
of the larger plots can be located
at vantage points throughout the
potential area being considered with
the objective of covering most of the
area of interest. Flight height should
also be collected to focus estimates
of use on activity occurring in the
rotor-swept zone.
Sampling duration and frequency
will be determined on a projectby-project basis and by the
questions being addressed. The
most important consideration for
sampling frequency when estimating
abundance is the amount of variation

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
expected among survey dates and
locations and the species of concern.

protocol for each site, including
timing and number of surveys
needed, search area, and search
techniques.

The use of comparable methods
and metrics should allow data
comparison from plot to plot within
the area of interest and from site to
site where similar data exist. The
data should be collected so that avian
activity can be estimated within
the rotor-swept zone. Relating
use to site characteristics requires
that samples of use also measure
site characteristics thought to
influence use (i.e., covariates such
as vegetation and topography) in
relation to the location of use. The
statistical relationship of use to these
covariates can be used to predict
occurrence in unsurveyed areas
during the survey period and for the
same areas in the future.
Surveys should be conducted at
different intervals during the year
to account for variation in expected
bird activity with lower frequency
during winter months if avian
activity is low. Sampling frequency
should also consider the episodic
nature of activity during fall and
spring migration. Standardized
protocols for estimating avian
abundance are well-established and
should be consulted (e.g., Dettmers
et al. 1999). If a more precise
estimate of density is required for
a particular species (e.g., when the
goal is to determine densities of a
special-status breeding bird species),
the researcher will need more
sophisticated sampling procedures,
including estimates of detection
probability.
Raptor Nest Searches
An estimate of raptor use of the
project site is obtained through
appropriate surveys, but if potential
impacts to breeding raptors are a
concern on a project, raptor nest
searches are also recommended.
These surveys provide information
to predict risk to the local
breeding population of raptors,
for micro-siting decisions, and for
developing an appropriate-sized
non-disturbance buffer around
nests. Surveys also provide
baseline data for estimating
impacts and determining mitigation

Prairie Grouse and Sage Grouse
Population Assessments
Sage grouse and prairie grouse
merit special attention in this
context for three reasons:
1. The scale and biotic nature
of their habitat requirements
uniquely position them as reliable
indicators of impacts on, and
needs of, a suite of species that
depend on sage and grassland
habitats, which are among
the nation’s most diminished
ecological communities (Vodehnal
and Haufler 2007).
Red-tailed hawk. Credit: Dave Menke, USFWS

requirements. A good source of
information for raptor surveys and
monitoring is Bird and Bildstein
(2007).
Searches for raptor nests or raptor
breeding territories on projects
with potential for impacts to raptors
should be conducted in suitable
habitat during the breeding season.
While there is no consensus on the
recommended buffer zones around
nest sites to avoid disturbance of
most species (Sutter and Jones
1981), a nest search within at least
one mile of the wind turbines
and transmission lines, and other
infrastructure should be conducted.
However, larger nest search areas
are needed for eagles, as explained
in the Service’s ECP Guidance, when
bald or golden eagles are likely to be
present.
Methods for these surveys are
fairly common and will vary with
the species, terrain, and vegetation
within the survey area. The Service
recommends that protocols be
discussed with biologists from the
lead agency, Service, state wildlife
agency, and Tribes where they have
jurisdiction. It may be useful to
consult other scientifically credible
information sources. At minimum,
the protocols should contain the
list of target raptor species for nest
surveys and the appropriate search

2. Their ranges and habitats are
highly congruent with the nation’s
richest inland wind resources.
3. They are species for which some
known impacts of anthropogenic
features (e.g., tall structures,
buildings, roads, transmission
lines, wind energy facilities, etc.)
have been documented.
Populations of prairie grouse and
sage grouse generally are assessed
by either lek counts (a count of
the maximum number of males
attending a lek) or lek surveys
(classification of known leks as active
or inactive) during the breeding
season (e.g., Connelly et al. 2000).
Methods for lek counts vary slightly
by species but in general require
repeated visits to known sites and
a systematic search of all suitable
habitat for leks, followed by repeated
visits to active leks to estimate the
number of grouse using them.
Recent research indicates that
viable prairie grouse and sage
grouse populations are dependent on
suitable nesting and brood-rearing
habitat (Connelly et al. 2000,
Hagen et al. 2009). These habitats
generally are associated with leks.
Leks are the approximate centers of
nesting and brood-rearing habitats
(Connelly et al. 2000, but see
Connelly et al. 1988 and Becker et
al. 2009). High quality nesting and
  29

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
brood rearing habitats surrounding
leks are critical to sustaining viable
prairie grouse and sage grouse
populations (Giesen and Connelly
1993, Hagen et al. 2004, Connelly et
al. 2000). A population assessment
study area should include nesting
and brood rearing habitats that may
extend several miles from leks. For
example, greater and lesser prairiechickens generally nest in suitable
habitats within one to two miles
of active leks (Hagen et al. 2004),
whereas the average distances from
nests to active leks of non-migratory
sage grouse range from 0.7 to four
miles (Connelly et al. 2000), and
potentially much more for migratory
populations (Connelly et al. 1988).
While surveying leks during the
spring breeding season is the most
common and convenient tool for
monitoring population trends of
prairie grouse and sage grouse,
documenting available nesting and
brood rearing habitat within and
adjacent to the potentially affected
area is recommended. Suitable
nesting and brood rearing habitats
can be mapped based on habitat
requirements of individual species.
The distribution and abundance
of nesting and brood rearing
habitats can be used to help in the
assessment of adverse impacts of the
proposed project to prairie grouse
and sage grouse.
Mist-Netting for Birds
Mist-netting is not recommended as
a method for assessing risk of wind
development for birds. Mist-netting
cannot generally be used to develop
indices of relative bird abundance,
nor does it provide an estimate of
collision risk as mist-netting is not
feasible at the heights of the rotorswept zone and captures below that
zone may not adequately reflect
risk. Operating mist-nets requires
considerable experience, as well as
state and federal permits.
Occasionally mist-netting can help
confirm the presence of rare species
at documented fallout or migrant
stopover sites near a proposed
project. If mist-netting is to be
used, the Service recommends
that procedures for operating nets
30 

and collecting data be followed in
accordance with Ralph et al. (1993).
Nocturnal and Crepuscular Bird
Survey Methods
Additional studies using different
methods should be conducted if
characteristics of the project site
and surrounding areas potentially
pose a high risk of collision to night
migrating songbirds and other
nocturnal or crepuscular species.
For most of their flight, songbirds
and other nocturnal migrants are
above the reach of wind turbines,
but they pass through the altitudinal
range of wind turbines during
ascents and descents and may also
fly closer to the ground during
inclement weather (Able, 1970;
Richardson, 2000). Factors affecting
flight path, behavior, and “fall-out”
locations of nocturnal migrants are
reviewed elsewhere (e.g., Williams
et al., 2001; Gauthreaux and Belser,
2003; Richardson, 2000; Mabee et al.,
2006).
In general, pre-construction
nocturnal studies are not
recommended unless the site
has features that might strongly
concentrate nocturnal birds,
such as along coastlines that are
known to be migratory songbird
corridors. Biologists knowledgeable
about nocturnal bird migration
and familiar with patterns of
migratory stopovers in the region
should assess the potential risks to
nocturnal migrants at a proposed
project site. No single method can
adequately assess the spatial and
temporal variation in nocturnal
bird populations or the potential
collision risk. Following nocturnal
study methods in Kunz et al. (2007)
is recommended to determine
relative abundance, flight direction
and flight altitude for assessing risk
to migrating birds, if warranted.
If areas of interest are within the
range of nocturnal species of concern
(e.g., marbled murrelet, northern
spotted owl, Hawaiian petrel,
Newell’s shearwater), surveyors
should use species-specific protocols
recommended by state wildlife
agencies, Tribes or Service to assess
the species’ potential presence in the
area of interest.

In contrast to the diurnal avian
survey techniques previously
described, considerable variation
and uncertainty exist on the
optimal protocols for using acoustic
monitoring devices, radar, and
other techniques to evaluate species
composition, relative abundance,
flight height, and trajectory of
nocturnal migrating birds. While
an active area of research, the use
of radar for determining passage
rates, flight heights and flight
directions of nocturnal migrating
animals has yet to be shown as
a good indicator of collision risk.
Pre- and post-construction studies
comparing radar monitoring results
to estimates of bird and bat fatalities
will be necessary to evaluate radar
as a tool for predicting collision risk.
Additional studies are also needed
before making recommendations on
the number of nights per season or
the number of hours per night that
are appropriate for radar studies of
nocturnal bird migration (Mabee et
al., 2006).
Bat survey methods
The Service recommends that all
techniques discussed below be
conducted by biologists trained in
bat identification, equipment use,
and the analysis and interpretation
of data resulting from the design and
conduct of the studies. Activities
that involve capturing and handling
bats may require permits from state
and/or federal agencies.
Acoustic Monitoring
Acoustic monitoring provides
information about bat presence and
activity, as well as seasonal changes
in species occurrence and use, but
does not measure the number of
individual bats or population density.
The goal of acoustic monitoring is to
provide a prediction of the potential
risk of bat fatalities resulting from
the construction and operation
of a project. Our current state of
knowledge about bat-wind turbine
interactions, however, does not allow
a quantitative link between preconstruction acoustic assessments of
bat activity and operations fatalities.
Discussions with experts, state
wildlife trustee agencies, Tribes, and

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
samples (~1.5-2 meters) can provide
equal or greater correlation with
bat fatalities than “high” position
samples (described above) because
this would substantially lower cost
of this work. Developers could
then install a greater number of
detectors at lower cost resulting
in improved estimates of bat
activity and, potentially, improved
qualitative estimates of risk to bats.
This is a research question that is
not expected to be addressed at a
project.
Other bat survey techniques

Tri-colored bat. Credit: USFWS

Service will be needed to determine
whether acoustic monitoring is
warranted at a proposed project site.
The predominance of bat fatalities
detected to date are migratory
species and acoustic monitoring
should adequately cover periods
of migration and periods of known
high activity for other (i.e., nonmigratory) species. Monitoring
for a full year is recommended in
areas where there is year round
bat activity. Data on environmental
variables such as temperature and
wind speed should be collected
concurrently with acoustic
monitoring so these weather data
can be used in the analysis of bat
activity levels.
The number and distribution of
sampling stations necessary to
adequately estimate bat activity
have not been well established but
will depend, at least in part, on the
size of the project area, variability
within the project area, and a
Tier 2 assessment of potential bat
occurrence.
The number of detectors needed
to achieve the desired level of
precision will vary depending on the
within-site variation (e.g., Arnett
et al. 2006, Weller 2007, See also,
Bat Conservation International
website for up-to-date survey
methodologies). One frequently
used method is to place acoustic

detectors on existing met towers,
approximately every two kilometers
across the site where turbines are
expected to be sited. Acoustic
detectors should be placed at high
positions (as high as practicable,
based on tower height) on each
met tower included in the sample
to record bat activity at or near
the rotor swept zone, the area of
presumed greatest risk for bats.
Developers should evaluate whether
it would be cost effective to install
detectors when met towers are first
established on a site. Doing so might
reduce the cost of installation later
and might alleviate time delays to
conduct such studies.
If sampling at met towers does not
adequately cover the study area
or provide sufficient replication,
additional sampling stations can be
established at low positions (~1.5-2
meters) at a sample of existing met
towers and one or more mobile
units (i.e., units that are moved to
different locations throughout the
study period) to increase coverage
of the proposed project area. When
practical and based on information
from Tier 2, it may be appropriate
to conduct some acoustic monitoring
of features identified as potentially
high bat use areas within the study
area (e.g., bat roosts and caves) to
determine use of such features.
There is growing interest in
determining whether “low” position

Occasionally, other techniques
may be needed to answer Tier 3
questions and complement the
information from acoustic surveys.
Kunz et al. (2007), NAS (2007),
Kunz and Parsons (2009) provide
comprehensive descriptions of bat
survey techniques, including those
identified below that are relevant
for Tier 3 studies at wind energy
facilities.
Roost Searches and Exit Counts
Pre-construction survey efforts
may be recommended to determine
whether known or likely bat roosts
in mines, caves, bridges, buildings,
or other potential roost sites occur
within the project vicinity, and to
confirm whether known or likely bat
roosts are present and occupied by
bats. If active roosts are detected,
it may be appropriate to address
questions about colony size and
species composition of roosts. Exit
counts and roost searches are two
approaches to answering these
questions, and Rainey (1995), Kunz
and Parsons (2009), and Sherwin et
al. (2009) are resources that describe
options and approaches for these
techniques. Roost searches should
be performed cautiously because
roosting bats are sensitive to human
disturbance (Kunz et al. 1996).
Known maternity and hibernation
roosts should not be entered
or otherwise disturbed unless
authorized by state and/or federal
wildlife agencies. Internal searches
of abandoned mines or caves can
be dangerous and should only be
conducted by trained researchers.
For mine survey protocol and
  31

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
guidelines for protection of bat
roosts, see the appendices in Pierson
et al. (1999). Exit surveys at known
roosts generally should be limited to
non-invasive observation using lowlight binoculars and infrared video
cameras.
Multiple surveys should be
conducted to determine the presence
or absence of bats in caves and
mines, and the number of surveys
needed will vary by species of bats,
sex (maternity or bachelor colony)
of bats, seasonality of use, and type
of roost structure (e.g., caves or
mines). For example, Sherwin et al.
(2003) demonstrated that a minimum
of three surveys are needed to
determine the absence of large
hibernating colonies of Townsend’s
big-eared bats in mines (90 percent
probability), while a minimum of
nine surveys (during a single warm
season) are necessary before a mine
could be eliminated as a bachelor
roost for this species (90 percent
probability). An average of three
surveys was needed before surveyed
caves could be eliminated as bachelor
roosts (90 percent probability). The
Service recommends that decisions
on level of effort follow discussion
with relevant agencies and bat
experts.

Activity Patterns
If active roosts are detected, it may
be necessary to answer questions
about behavior, movement patterns,
and patterns of roost use for bat
species of concern, or to further
investigate habitat features that
might attract bats and pose fatality
risk. For some bat species, typically
threatened, endangered, or statelisted species, radio telemetry
or radar may be recommended
to assess both the direction of
movement as bats leave roosts,
and the bats’ use of the area being
considered for development. Kunz
et al. (2007) describe the use of
telemetry, radar and other tools
to evaluate use of roosts, activity
patterns, and flight direction from
roosts.
Mist-Netting for Bats
While mist-netting for bats is
required in some situations by
state agencies, Tribes, and the
Service to determine the presence
of threatened, endangered or other
bat species of concern, mist-netting
is not generally recommended
for determining levels of activity
or assessing risk of wind energy

development to bats for the following
reasons: 1) not all proposed or
operational wind energy facilities
offer conditions conducive to
capturing bats, and often the
number of suitable sampling points
is minimal or not closely associated
with the project location; 2) capture
efforts often occur at water sources
offsite or at nearby roosts and the
results may not reflect species
presence or use on the site where
turbines are to be erected; and 3)
mist-netting isn’t feasible at the
height of the rotor-swept zone, and
captures below that zone may not
adequately reflect risk of fatality. If
mist-netting is employed, it is best
used in combination with acoustic
monitoring to inventory the species
of bats present at a site.
White-Nose Syndrome
White-nose syndrome is a disease
affecting hibernating bats. Named
for the white fungus that appears
on the muzzle and other body
parts of hibernating bats, WNS is
associated with extensive mortality
of bats in eastern North America.
All contractors and consultants
hired by developers should employ
the most current version of survey
and handling protocols to avoid
transmitting white-nose syndrome
between bats.
Other wildlife

Mule deer. Credit: Tupper Ansel Blake, USFWS

32 

While the above guidance
emphasizes the evaluation of
potential impacts to birds and
bats, Tier 1 and 2 evaluations may
identify other species of concern.
Developers are encouraged to
assess adverse impacts potentially
caused by development for
those species most likely to be
negatively affected by such
development. Impacts to other
species are primarily derived
from potential habitat loss or
displacement. The general
guidance on the study design and
methods for estimation of the
distribution, relative abundance,
and habitat use for birds is
applicable to the study of other
wildlife. References regarding
monitoring for other wildlife
are available in Appendix C:

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Sources of Information Pertaining
to Methods to Assess Impacts
to Wildlife. Nevertheless, most
methods and metrics will be speciesspecific and developers are advised
to work with the state, tribal, or
federal agencies, or other credible
experts, as appropriate, during
problem formulation for Tier 3.

Tier 3 Decision Points
Developers and the Service should
communicate prior to completing
the Tier 3 decision process. A
developer should inform the Service
of the results of its studies and
plans. The Service will provide
written comments to a developer
on study and project development
plans that identify concerns and
recommendations to resolve the
concerns. The developer and, when
applicable, the permitting authority
will make a decision regarding
whether and how to develop the
project. The decision point at the
end of Tier 3 involves three potential
outcomes:
1. Development of the site has a low
probability of significant adverse
impact based on existing and new
information.
There is little uncertainty
regarding when and how
development should proceed, and
adequate information exists to
satisfy any required permitting.
The decision process proceeds to
permitting, when required, and/or
development, and Tier 4.
2. Development of the site has a
moderate to high probability
of significant adverse impacts
without proper measures being
taken to mitigate those impacts.
This outcome may be subdivided
into two possible scenarios:
a. There is certainty regarding
how to develop the site
to adequately mitigate
significant adverse impacts.
The developer bases their
decision to develop the site
adopting proper mitigation
measures and appropriate
post-construction fatality and
habitat studies (Tier 4).

Little brown bat with white nose syndrome. Credit: Marvin Moriarty, USFWS

b. There is uncertainty
regarding how to develop the
site to adequately mitigate
significant adverse impacts, or
a permitting process requires
additional information on
potential significant adverse
wildlife impacts before
permitting future phases of
the project. The developer
bases their decision to develop
the site adopting proper
mitigation measures and
appropriate post-construction
fatality and habitat studies
(Tier 4).

begins an evaluation of other sites
or landscapes for more acceptable
sites to develop.
b. Can be adequately mitigated.
Developer should implement
mitigation measures and proceed
to Tier 4.

3. Development of the site has a
high probability of significant
impact that:
a. Cannot be adequately
mitigated.
Site development should be
delayed until plans can be
developed that satisfactorily
mitigate for the significant
adverse impacts. Alternatively,
the site should be abandoned in
favor of known sites with less
potential for environmental
impact, or the developer
  33

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 5: Tier 4 – Post-construction Studies to
Estimate Impacts
The outcome of studies in Tiers
1, 2, and 3 will determine the
duration and level of effort of postconstruction studies.
Tier 4 post-construction studies
are designed to assess whether
predictions of fatality risk and direct
and indirect impacts to habitat of
species of concern were correct.
Fatality studies involve searching
for bird and bat carcasses beneath
turbines to estimate the number
and species composition of fatalities
(Tier 4a). Habitat studies involve
application of GIS and use data
collected in Tier 3 and Tier 4b and/
or published information. Postconstruction studies on direct and
indirect impacts to habitat of species
of concern, including species of
habitat fragmentation concern need
only be conducted if Tier 3 studies
indicate the potential for significant
adverse impacts.

Tier 4a – Fatality Studies
At this time, community- and utilityscale projects should conduct at
least one year of fatality monitoring.
The intensity of the studies should
be related to risks of significant
adverse impacts identified in preconstruction assessments. As data
collected with consistent methods
and metrics increases (see discussion
below), it is possible that some future
projects will not warrant fatality
monitoring, but such a situation
is rare with the present state of
knowledge.
Fatality monitoring should occur
over all seasons of occupancy for the
species being monitored, based on
information produced in previous
tiers. The number of seasons and
total length of the monitoring
may be determined separately for
bats and birds, depending on the
pre-construction risk assessment,
results of Tier 3 studies and Tier 4
monitoring from comparable sites
(see Glossary in Appendix A) and
34 

A male Eastern red bat perches among green foliage. Credit: ©MerlinD.Tuttle,BatConservationInternatio
nal,www.batcon.org

the results of first year fatality
monitoring. Guidance on the
relationship between these variables
and monitoring for fatalities is
provided in Table 2.
It may be appropriate to conduct
monitoring using different durations

and intervals depending on the
species of concern. For example, if
raptors occupy an area year-round,
it may be appropriate to monitor
for raptors throughout the year
(12 months). It may be warranted
to monitor for bats when they are
active (spring, summer and fall or

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
approximately eight months). It
may be appropriate to increase
the search frequency during the
months bats are active and decrease
the frequency during periods of
inactivity. All fatality monitoring
should include estimates of carcass
removal and carcass detection bias
likely to influence those rates.
Tier 4a Questions
Post-construction fatality monitoring
should be designed to answer the
following questions as appropriate
for the individual project:
1. What are the bird and bat
fatality rates for the project?
2. What are the fatality rates of
species of concern?
3. How do the estimated fatality
rates compare to the predicted
fatality rates?
4. Do bird and bat fatalities
vary within the project site in
relation to site characteristics?
5. How do the fatality rates
compare to the fatality rates
from existing projects in similar
landscapes with similar species
composition and use?
6. What is the composition
of fatalities in relation to
migrating and resident birds
and bats at the site?
7. Do fatality data suggest the
need for measures to reduce
impacts?
Tier 4a studies should be of
sufficient statistical validity to
address Tier 4a questions and
enable determination of whether
Tier 3 fatality predictions were
correct. Fatality monitoring results
also should allow comparisons with
other sites, and provide a basis for
determining if operational changes
or other mitigation measures at the
site are appropriate. The Service
encourages project operators to
discuss Tier 4 studies with local,
state, federal, and tribal wildlife
agencies. The number of years of
monitoring is based on outcomes of

Tier 3 and Tier 4 studies and analysis
of comparable Tier 4 data from other
projects as indicated in Table 2. The
Service may recommend multiple
years of monitoring for projects
located near a listed species or bald
or golden eagle, or other situations,
as appropriate.
Tier 4a Protocol Design
Considerations
The basic method of measuring
fatality rates is the carcass
search. Search protocols should be
standardized to the greatest extent
possible, especially for common
objectives and species of concern,
and they should include methods
for adequately accounting for
sampling biases (searcher efficiency
and scavenger removal). However,
some situations warrant exceptions
to standardized protocol. The
responsibility of demonstrating
that an exception is appropriate and
applicable should be on the project
operator to justify increasing or
decreasing the duration or intensity
of operations monitoring.
Some general guidance is given
below with regard to the following
fatality monitoring protocol design
issues:
• Duration and frequency of
monitoring
• Number of turbines to monitor
• Delineation of carcass search
plots, transects, and habitat
mapping
• General search protocol
• Field bias and error
assessment
• Estimators of fatality
More detailed descriptions
and methods of fatality search
protocols can be found in the
California (California Energy
Commission 2007) and Pennsylvania
(Pennsylvania Game Commission
2007) state guidelines and in Kunz
et al. (2007), Smallwood (2007), and
Strickland et al. (2011).

Duration and frequency of
monitoring
Frequency of carcass searches
(search interval) may vary for birds
and bats, and will vary depending
on the questions to be answered,
the species of concern, and their
seasonal abundance at the project
site. The carcass searching protocol
should be adequate to answer
applicable Tier 4 questions at
an appropriate level of precision
to make general conclusions
about the project, and is not
intended to provide highly precise
measurements of fatalities. Except
during low use times (e.g. winter
months in northern states), the
Service recommends that protocols
be designed such that carcass
searches occur at some turbines
within the project area most days
each week of the study.
The search interval is the interval
between carcass searches at
individual turbines, and this interval
may be lengthened or shortened
depending on the carcass removal
rates. If the primary focus is on
fatalities of large raptors, where
carcass removal is typically low, then
a longer interval between searches
(e.g., 14-28 days) is sufficient.
However, if the focus is on fatalities
of bats and small birds and carcass
removal is high, then a shorter
search interval will be necessary.
There are situations in which
studies of higher intensity (e.g.,
daily searches at individual
turbines within the sample) may
be appropriate. These would be
considered only in Tier 5 studies or
in research programs because the
greater complexity and level of effort
goes beyond that recommended
for typical Tier 4 post construction
monitoring. Tier 5 and research
studies could include evaluation of
specific measures that have been
implemented to mitigate potential
significant adverse impacts to
species of concern identified during
pre-construction studies.
Number of turbines to monitor
If available, data on variability
among turbines from existing
  35

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Evidence suggests that greater
than 80 percent of bat fatalities fall
within half the maximum distance of
turbine height to ground (Erickson
2003 a, b), and a minimum plot width
of 120 meters from the turbine
should be established at sample
turbines. Plots will need to be larger
for birds, with a width twice the
turbine height to ground. Decisions
regarding search plot size should be
made in discussions with the Service,
state wildlife agency, permitting
agency and Tribes. It may be
useful to consult other scientifically
credible information sources.

Wind turbine. Credit: NREL

projects in similar conditions within
the same region are recommended
as a basis for determining needed
sample size (see Morrison et al.,
2008). If data are not available,
the Service recommends that
an operator select a sufficient
number of turbines via a systematic
sample with a random start point.
Sampling plans can be varied (e.g.,
rotating panels [McDonald 2003,
Fuller 1999, Breidt and Fuller
1999, and Urquhart et al. 1998])
to increase efficiency as long as
a probability sampling approach
is used. If the project contains
fewer than 10 turbines, the Service
recommends that all turbines in
the area of interest be searched
unless otherwise agreed to by the
permitting or wildlife resource
agencies. When selecting turbines,
the Service recommends that a
systematic sample with a random
start be used when selecting search
plots to ensure interspersion
among turbines. Stratification
among different habitat types also
is recommended to account for
differences in fatality rates among
different habitats (e.g., grass versus
cropland or forest); a sufficient
number of turbines should be
sampled in each strata.
Delineation of carcass search plots,
transects, and habitat mapping
36 

The Service recommends that each
search plot should be divided into
oblong subplots or belt transects
and that each subplot be searched.
The objective is to find as many
carcasses as possible so the width of
the belt will vary depending on the
ground cover and its influence on
carcass visibility. In most situations,
a search width of 6 meters should
be adequate, but this may vary from
3-10 meters depending on ground
cover.
Searchable area within the
theoretical maximum plot size
varies, and heavily vegetated areas
(e.g., eastern mountains) often do
not allow surveys to consistently
extend to the maximum plot width.
In other cases it may be preferable
to search a portion of the maximum
plot instead of the entire plot. For
example, in some landscapes it may
be impractical to search the entire
plot because of the time required
to do an effective search, even if it
is accessible (e.g., croplands), and
data from a probability sample
of subplots within the maximum
plot size can provide a reasonable
estimate of fatalities. It is important
to accurately delineate and map the
area searched for each turbine to
adjust fatality estimates based on
the actual area searched. It may
be advisable to establish habitat
visibility classes in each plot to
account for differential detectability,
and to develop visibility classes for
different landscapes (e.g., rocks,
vegetation) within each search plot.
For example, the Pennsylvania Game
Commission (2007) identified four
classes based on the percentage of

bare ground.
The use of visibility classes requires
that detection and removal biases
be estimated for each class. Fatality
estimates should be made for each
class and summed for the total area
sampled. Global positioning systems
(GPS) are useful for accurately
mapping the actual total area
searched and area searched in each
habitat visibility class, which can
be used to adjust fatality estimates.
The width of the belt or subplot
searched may vary depending on the
habitat and species of concern; the
key is to determine actual searched
area and area searched in each
visibility class regardless of transect
width. An adjustment may also
be needed to take into account the
density of fatalities as a function of
the width of the search plot.
General search protocol
Personnel trained in proper search
techniques should look for bird
and bat carcasses along transects
or subplots within each plot and
record and collect all carcasses
located in the searchable areas. The
Service will work with developers
and operators to provide necessary
permits for carcass possession. A
complete search of the area should
be accomplished and subplot
size (e.g., transect width) should
be adjusted to compensate for
detectability differences in the
search area. Subplots should be
smaller when vegetation makes
it difficult to detect carcasses;
subplots can be wider in open
terrain. Subplot width also can vary
depending on the size of the species
being looked for. For example, small
species such as bats may require
smaller subplots than larger species
such as raptors.
Data to be recorded include date,
start time, end time, observer,
which turbine area was searched
(including GPS coordinates) and
weather data for each search.
When a dead bat or bird is found,
the searcher should place a flag
near the carcass and continue the
search. After searching the entire
plot, the searcher returns to each
carcass and records information

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
on a fatality data sheet, including
date, species, sex and age (when
possible), observer name, turbine
number, distance from turbine,
azimuth from turbine (including GPS
coordinates), habitat surrounding
carcass, condition of carcass (entire,
partial, scavenged), and estimated
time of death (e.g., <1 day, 2 days).
The recorded data will ultimately
be housed in the FWS Office of
Law Enforcement Bird Mortality
Reporting System. A digital
photograph of the carcass should be
taken. Rubber gloves should be used
to handle all carcasses to eliminate
possible transmission of rabies or
other diseases and to reduce possible
human scent bias for carcasses
later used in scavenger removal
trials. Carcasses should be placed
in a plastic bag and labeled. Unless
otherwise conditioned by the carcass
possession permit, fresh carcasses
(those determined to have been
killed the night immediately before
a search) should be redistributed at
random points on the same day for
scavenging trials.
Field bias and error assessment
During searches conducted at wind
turbines, actual fatalities are likely
incompletely observed. Therefore
carcass counts must be adjusted
by some factor that accounts for
imperfect detectability (Huso
2011). Important sources of bias
and error include: 1) fatalities that
occur on a highly periodic basis; 2)
carcass removal by scavengers; 3)
differences in searcher efficiency; 4)
failure to account for the influence
of site (e.g. vegetation) conditions
in relation to carcass removal and
searcher efficiency; and 5) fatalities
or injured birds and bats that may
land or move outside search plots.
Some fatalities may occur on a
highly periodic basis creating a
potential sampling error (number
1 above). The Service recommends
that sampling be scheduled so that
some turbines are searched most
days and episodic events are more
likely detected, regardless of the
search interval. To address bias
sources 2-4 above, it is strongly
recommended that all fatality
studies conduct carcass removal

and searcher efficiency trials using
accepted methods (Anderson 1999,
Kunz et al. 2007, Arnett et al. 2007,
NRC 2007, Strickland et al. 2011).
Bias trials should be conducted
throughout the entire study period
and searchers should be unaware
of which turbines are to be used
or the number of carcasses placed
beneath those turbines during trials.
Carcasses or injured individuals
may land or move outside the search
plots (number 5 above). With
respect to Tier 4a fatality estimates,
this potential sampling error is
considered to be small and can be
assumed insignificant (Strickland et
al. 2011).
Prior to a study’s inception, a list
of random turbine numbers and
random azimuths and distances (in
meters) from turbines should be
generated for placement of each
bat or bird used in bias trials. Data
recorded for each trial carcass prior
to placement should include date of
placement, species, turbine number,
distance and direction from turbine,
and visibility class surrounding the
carcass. Trial carcasses should be
distributed as equally as possible
among the different visibility classes
throughout the study period and
study area. Studies should attempt
to avoid “over-seeding” any one
turbine with carcasses by placing
no more than one or two carcasses
at any one time at a given turbine.
Before placement, each carcass must
be uniquely marked in a manner that
does not cause additional attraction,
and its location should be recorded.
There is no agreed upon sample size
for bias trials, though some state
guidelines recommend from 50 - 200
carcasses (e.g., PGC 2007).
Estimators of fatality
If there were a direct relationship
between the number of carcasses
observed and the number killed,
there would be no need to develop
a complex estimator that adjusts
observed counts for detectability,
and observed counts could be
used as a simple index of fatality
(Huso 2011). But the relationship
is not direct and raw carcass
counts recorded using different
search intervals and under

different carcass removal rates
and searcher efficiency rates are
not directly comparable. It is
strongly recommended that only
the most contemporary equations
for estimating fatality be used, as
some original versions are now
known to be extremely biased under
many commonly encountered field
conditions (Erickson et al. 2000b,
Erickson et al. 2004, Johnson et al.
2003, Kerns and Kerlinger 2004,
Fiedler et al. 2007, Kronner et al.
2007, Smallwood 2007, Huso 2011,
Strickland et al. 2011).

Tier 4a Study Objectives
In addition to the monitoring
protocol design considerations
described above, the metrics used
to estimate fatality rates must be
selected with the Tier 4a questions
and objectives in mind. Metrics
considerations for each of the Tier
4a questions are discussed briefly
below. Not all questions will be
relevant for each project, and which
questions apply would depend on
Tier 3 outcomes.
1. What are the bird and bat
fatality rates for the project?
The primary objective of fatality
searches is to determine the overall
estimated fatality rates for birds and
bats for the project. These rates
serve as the fundamental basis for
all comparisons of fatalities, and if
studies are designed appropriately
they allow researchers to relate
fatalities to site characteristics
and environmental variables, and
to evaluate mitigation measures.
Several metrics are available for
expressing fatality rates. Early
studies reported fatality rates per
turbine. However, this metric is
somewhat misleading as turbine
sizes and their risks to birds vary
significantly (NRC 2007). Fatalities
are frequently reported per
nameplate capacity (i.e. MW), a
metric that is easily calculated and
better for comparing fatality rates
among different sized turbines.
Even with turbines of the same
name plate capacity, the size of the
rotor swept area may vary among
manufacturers, and turbines at
various sites may operate for
  37

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
different lengths of time and during
different times of the day and
seasons. With these considerations
in mind, the Service recommends
that fatality rates be expressed on a
per-turbine and per-nameplate MW
basis until a better metric becomes
available.
2. What are the fatality rates of
species of concern?
This analysis simply involves
calculating fatalities per turbine of
all species of concern at a site when
sample sizes are sufficient to do so.
These fatalities should be expressed
on a per nameplate MW basis if
comparing species fatality rates
among projects.
3. How do the estimated fatality
rates compare to the predicted
fatality rates?
There are several ways that
predictions can be evaluated
with actual fatality data. During
the planning stages in Tier 2,
predicted fatalities may be based
on existing data at similar facilities
in similar landscapes used by
similar species. In this case, the
assumption is that use is similar,
and therefore that fatalities may
be similar at the proposed facility.
Alternatively, metrics derived from
pre-construction assessments for
an individual species or group of
species – usually an index of activity
or abundance at a proposed project –
could be used in conjunction with use
and fatality estimates from existing
projects to develop a model for
predicting fatalities at the proposed
project site. Finally, physical models
can be used to predict the probability
of a bird of a particular size striking
a turbine, and this probability, in
conjunction with estimates of use
and avoidance behavior, can be used
to predict fatalities.
The most current equations for
estimating fatality should be used
to evaluate fatality predictions.
Several statistical methods can be
found in the revised Strickland et
7

al. 2011 and used to evaluate fatality
predictions. Metrics derived from
Tier 3 pre-construction assessments
may be correlated with fatality
rates, and (using the project as the
experimental unit), in Tier 5 studies
it should be possible to determine
if different preconstruction metrics
can in fact accurately predict
fatalities and, thus, risk.
4. Do bird and bat fatalities
vary within the project site in
relation to site characteristics?
Data from pre-construction
studies can demonstrate patterns
of activity that may depend upon
the site characteristics. Turbines
placed near escarpments or cliffs
may intrude upon airspace used by
raptors soaring on thermals. Preconstruction and post construction
studies and assessments can be used
to avoid siting individual, specific
turbines within an area used by
species of concern. Turbine-specific
fatality rates may be related to site
characteristics such as proximity
to water, forest edge, staging and
roosting sites, known stop-over
sites, or other key resources, and
this relationship may be estimated
using regression analysis. This
information is particularly useful
for evaluating micro-siting options
when planning a future facility or, on
a broader scale, in determining the
location of the entire project.
5. How do the fatality rates
compare to the fatality rates
from existing facilities in
similar landscapes with similar
species composition and use?
Comparing fatality rates among
facilities with similar characteristics
can be useful to determine patterns
and broader landscape relationships.
Developers should communicate
with the Service to ensure that
such comparisons are appropriate
to avoid false conclusions. Fatality
rates should be expressed on a
per nameplate MW or some other
standardized metric basis for
comparison with other projects,

Big brown bat. Credit: USFWS

and may be correlated with site
characteristics – such as proximity
to wetlands, riparian corridors,
mountain-foothill interface, wind
patterns, or other broader landscape
features – using regression analysis.
Comparing fatality rates from one
project to fatality rates of other
projects provides insight into
whether a project has relatively
high, moderate or low fatalities.
6. What is the composition
of fatalities in relation to
migrating and resident birds
and bats at the site?
The simplest way to address this
question is to separate fatalities per
turbine of known resident species
(e.g., big brown bat, prairie horned
lark) and those known to migrate
long distances (e.g. hoary bat, redeyed vireo). These data are useful
in determining patterns of species
composition of fatalities and possible
mitigation measures directed at
residents, migrants, or perhaps
both, and can be used in assessing
potential population effects.

In situations where a project operator was not the developer, the Service expects that obligations of the developer for adhering to the Guidelines
transfer with the project.

38 

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Table 2. Decision Framework for Tier 4a Fatality Monitoring of Species of Concern.8
Probability
of Significant
Adverse Impacts
in Tier 3

Recommended Fatality Monitoring
Duration and Effort

Possible Outcomes of Monitoring Results

Tier 3 Studies
indicate LOW
probability
of significant
adverse impacts

Duration: At least one year of fatality monitoring
to estimate fatalities of birds and bats. Field
assessments should be sufficient to confirm that risk
to birds and/or bats is indeed “low.”

1. Documented fatalities are approximately equal
to or lower than predicted risk. No further
fatality monitoring or mitigation is needed.
2. Fatalities are greater than predicted, but are
not likely to be significant (i.e., unlikely to
affect the long-term status of the population).
If comparable fatality data at similar sites
also supports that impacts are not likely to
be high enough to affect population status, no
further monitoring or mitigation is needed. If
no comparable fatality data are available or
such data indicates high risk, one additional
year of fatality monitoring is recommended.
If two years of fatality monitoring indicate
levels of impacts that are not significant, no
further fatality monitoring or mitigation is
recommended.
3. Fatalities are greater than predicted and are
likely to be significant OR federally endangered
or threatened species or BGEPA species are
affected. Communication with the Service
is recommended. Further efforts to address
impacts to BGEPA or ESA species may be
warranted, unless otherwise addressed in an
ESA or BGEPA take permit.

Tier 3 studies
indicate
MODERATE
probability
of significant
adverse impacts

Tier 3 studies
indicate HIGH
probability
of significant
adverse impacts

Duration: Two or more years of fatality monitoring
may be necessary.
Field assessments should be sufficient to confirm
that risk to birds and/or bats is indeed “moderate.”
Closely compare estimated effects to species to those
determined from the risk assessment protocol(s).

Duration: Two or more years of fatality monitoring
may be necessary to document fatality patterns.
If fatality is high, developers should shift emphasis
to exploring opportunities for mitigation rather than
continuing to monitor fatalities. If fatalities are
variable, additional years are likely warranted.

1. Documented fatalities after the first two years
are lower or not different than predicted and
are not significant and no federally endangered
species or BGEPA species are affected - no
further fatality monitoring or mitigation is
needed.
2. Fatalities are greater than predicted and are
likely to be significant OR federally endangered
or threatened species or BGEPA species are
affected, communication with the Service is
recommended. Further efforts to address
impacts to BGEPA or ESA species may be
warranted, unless otherwise addressed in an
ESA or BGEPA take permit.
1. Documented fatalities during each year of
fatality monitoring are less than predicted and
are not likely to be significant, and no federally
endangered or threatened species or BGEPA
species are affected – no further fatality
monitoring or mitigation is needed.
2. Fatalities are equal to or greater than predicted
and are likely to be significant - further efforts
to reduce impacts are necessary; communication
with the Service are recommended. Further
efforts, such as Tier 5 studies, to address
impacts to BGEPA or ESA species may be
warranted, unless otherwise addressed in an
ESA or BGEPA take permit.

8

Ensure that survey protocols, and searcher efficiency and scavenger removal bias correction factors are the most reliable, robust, and up to date
(after Huso 2009).

  39

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
7. Do fatality data suggest the
need for measures to reduce
impacts?
The Service recommends that
the wind project operator7 and
the relevant agencies discuss the
results from Tier 4 studies to
determine whether these impacts
are significant. If fatalities are
considered significant, the wind
project operator and the relevant
agencies should develop a plan to
mitigate the impacts.

Tier 4b – Assessing direct and
indirect impacts of habitat loss,
degradation, and fragmentation
The objective of Tier 4b studies is to
evaluate Tier 3 predictions of direct
and indirect impacts to habitat and
the potential for significant adverse
impacts on species of concern as
a result of these impacts. Tier 4b
studies should be conducted if Tier
3 studies indicate the presence of
species of habitat fragmentation
concern, or if Tier 3 studies indicate
significant direct and indirect
adverse impacts to species of
concern (see discussion below).
Tier 4b studies should also inform
project operators and the Service as
to whether additional mitigation is
necessary.

concern, and the project was
altered to mitigate for adverse
impacts, were those efforts
successful?
The answers to these questions will
be based on information estimating
habitat loss, degradation, and
fragmentation information collected
in Tier 3, currently available
demographic and genetic data, and
studies initiated in Tier 3. As in the
case of Tier 4a, the answers to these
questions will determine the need to
conduct Tier 5 studies. For example,
in the case that significant adverse
impacts to species of concern were
predicted, but mitigation was not
successful, then additional mitigation
and Tier 5 studies may be necessary.
See Table 3 for further guidance.
1. How do post-construction
habitat quality and spatial
configuration of the study area
compare to predictions for
species of concern identified in
Tier 3 studies?

1. How do post-construction
habitat quality and spatial
configuration of the study area
compare to predictions for
species of concern identified in
Tier 3 studies?

GIS and demographic data
collected in Tier 3 and/or
published information can be
used to determine predictions of
impacts to species of concern from
habitat loss, degradation, and
fragmentation. The developer can
provide development assumptions
based on Tier 3 information that can
be compared to post-construction
information. Additional postconstruction studies on impacts to
species of concern due to direct and
indirect impacts to habitat should
only be conducted if Tier 3 studies
indicate the potential for significant
adverse impacts.

2. Were any behavioral
modifications or indirect
impacts noted in regard to
species of concern?

2. Were any behavioral
modifications or indirect
impacts noted in regard to
affected species?

3. If significant adverse impacts
were predicted for species of
concern, and the project was
altered to mitigate for adverse
impacts, were those efforts
successful?

Evaluation of this question is based
on the analysis of observed use of
the area by species of concern prior
to construction in comparison with
observed use during operation.
Observations and demographic
data collected during Tier 3, and
assessment of published information
about the potential for displacement

Tier 4b studies should evaluate the
following questions:

4. If significant adverse impacts
were predicted for species of
40 

and demographic responses to habit
impacts could be the basis for this
analysis. If this analysis suggests
that direct and/or indirect loss of
habitat for a species of concern
leads to behavioral modifications or
displacement that are significant,
further studies of these impacts in
Tier 5 may be appropriate.
3. If significant adverse impacts
were not predicted in Tier 3
because of loss, degradation, or
fragmentation of habitat, but
Tier 4b studies indicate such
impacts have the potential to
occur, can these impacts be
mitigated?
When Tier 4b studies indicate
significant impacts may be
occurring, the developer may need
to conduct an assessment of these
impacts and what opportunities exist
for additional mitigation.
4. If significant adverse impacts
were predicted for species of
concern, and the project was
altered to mitigate for adverse
impacts, were those efforts
successful?
When Tier 4b studies indicate
significant impacts may be
occurring, the developer may need
to conduct an assessment of these
impacts and what opportunities exist
for additional mitigation. Evaluation
of the effectiveness of mitigation is a
Tier 4 study and should follow design
considerations discussed in Tier 5
and from guidance in the scientific
literature (e.g. Strickland et al.
2011).
When Tier 3 studies identified
potential moderate or high risks
to species of concern that caused a
developer to incorporate mitigation
measures into the project, Tier
4b studies should evaluate the
effectiveness of those mitigation
measures. Determining such
effectiveness is important for the
project being evaluated to ascertain
whether additional mitigation
measures are appropriate as well
as informing future decisions about
how to improve mitigation at wind

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
energy facilities being developed.
Tier 4b Protocol Design
Considerations
Impacts to a species of concern
resulting from the direct and
indirect loss of habitat are important
and must be considered when a
wind project is being considered
for development. Some species of
concern are likely to occur at every
proposed wind energy facility.
This occurrence may range from
a breeding population, to seasonal
occupancy, such as a brief occurrence
while migrating through the area.
Consequently the level of concern
regarding impacts due to direct
and indirect loss of habitat will vary
depending on the species and the
impacts that occur.
If a breeding population of a species
of habitat fragmentation concern
occurs in the project area and Tier 3
studies indicate that fragmentation
of their habitat is possible, these
predictions should be evaluated
following the guidance indicated in
Table 3 using the protocols described
in Tier 3. If the analysis of postconstruction GIS data on direct
and indirect habitat loss suggests
that fragmentation is likely, then
additional displacement studies
and mitigation may be necessary.
These studies would typically
begin immediately and would be
considered Tier 5 studies using
design considerations illustrated by
examples in Tier 5 below and from
guidance in the scientific literature
(e.g. Strickland et al. 2011).
Significant direct or indirect loss of
habitat for a species of concern may
occur without habitat fragmentation
if project impacts result in the
reduction of a habitat resource
that potentially is limiting to the
affected population. Impacts of this
type include loss of use of breeding
habitat or loss of a significant portion
of the habitat of a federally or state
protected species. This would
be evaluated by determining the
amount of the resource that is lost
and determining if this loss would
potentially result in significant
impacts to the affected population.
Evaluation of potential significant

Black-capped Vireo. Credit: Greg W. Lasley

impacts would occur in Tier 5 studies
that measure the demographic
response of the affected population.
The intention of the Guidelines is to
focus industry and agency resources
on the direct and indirect loss of
habitat and limiting resources that
potentially reduce the viability of a
species of concern. Not all direct
and indirect loss of a species’ habitat
will affect limiting resources for that
species, and when habitat losses are
minor or non-existent no further
study is necessary.
Tier 4b Decision Points
The developer should use the
results of the Tier 4b studies to
evaluate whether further studies
and/or mitigation are needed. The
developer should communicate
the results of these studies, and
decisions about further studies and
mitigation, with the Service. Table 3
provides a framework for evaluating
the need for further studies and
mitigation. Level of effort for
studies should be sufficient to answer
all questions of interest. Refer to the
relevant methods sections for Tier
2 Question 5 and Tier 3 Question 2
in the text for specific guidance on
study protocols.

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Table 3. Decision Framework to Guide Studies for Minimizing Impacts to Habitat and Species of Habitat Fragmentation
(HF) Concern.
Outcomes of Tier 2

Outcomes of Tier 3

Outcomes of Tier 4b

Suggested Study/Mitigation

• No species of HF concern
potentially present

• No further studies needed

• n/a

• n/a

• Species of HF concern
potentially present

• No species of HF concern
confirmed to be present

• No further studies needed

• n/a

• Species of HF concern
demonstrated to be
present, but no significant
adverse impacts predicted

• Tier 4b studies confirm
Tier 3 predictions

• No further studies or
mitigation needed

• Tier 4b studies indicate
potentially significant
adverse impacts

• Tier 5 studies and
mitigation may be needed

• Species of HF concern
potentially present

• Tier 4b studies determine
• Species of HF concern
mitigation plan is effective;
demonstrated to be
no significant adverse
present; significant adverse
impacts demonstrated
impacts predicted
• Mitigation plan developed
and implemented

42 

• Tier 4b studies determine
mitigation plan is NOT
effective; potentially
significant adverse impacts

• No further studies or
mitigation needed
• Further mitigation and,
where appropriate, Tier 5
studies

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 6: Tier 5 – Other Post-construction Studies
Tier 5 studies will not be necessary
for most wind energy projects. Tier
5 studies can be complex and time
consuming. The Service anticipates
that the tiered approach will steer
projects away from sites where Tier
5 studies would be necessary.

2. Were mitigation measures
implemented (other than fee
in lieu) not effective? This
includes habitat mitigation
measures as well as measures
undertaken to reduce collision
fatalities.

When Tier 5 studies are conducted,
they should be site-specific and
intended to: 1) analyze factors
associated with impacts in those
cases in which Tier 4 analyses
indicate they are potentially
significant; 2) identify why mitigation
measures implemented for a
project were not adequate; and 3)
assess demographic effects on local
populations of species of concern
when demographic information
is important, including species of
habitat fragmentation concern.

Tier 4a and b studies can assess the
effectiveness of measures taken to
reduce direct and indirect impacts
as part of the project and to identify
such alternative or additional
measures as are necessary. If
alternative or additional measures
were unsuccessful, the reasons why

would be evaluated using Tier 5
studies.
3. Are the estimated impacts of
the proposed project likely to
lead to population declines in
the species of concern (other
than federally-listed species)?
Impacts of a project will have
population level effects if the project
causes a population decline in the
species of concern. For non-listed
species, this assessment will apply
only to the local population.

Tier 5 Questions
Tier 5 studies are intended to answer
questions that fall in three major
categories; answering yes to any of
these questions might indicate a Tier
5 study is needed:
1. To the extent that the observed
fatalities exceed anticipated
fatalities, are those fatalities
potentially having a significant
adverse impact on local
populations? Are observed
direct and indirect impacts to
habitat having a significant
adverse impact on local
populations?
For example, in the Tier 3 risk
assessment, predictions of collision
fatalities and habitat impacts
(direct and indirect) are developed.
Post-construction studies in Tier
4 evaluate the accuracy of those
predictions by estimating impacts.
If post-construction studies
demonstrate potentially significant
adverse impacts, Tier 5 studies may
also be warranted and should be
designed to understand observed
versus predicted impacts.

Wind turbines and habitat. Credit: NREL

  43

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Tier 5 studies may need to be
conducted when:
• Realized fatality levels for
individual species of concern
reach a level at which they are
considered significant adverse
impacts by the relevant agencies.
For example, if Tier 4a fatality
studies document that a particular
turbine or set of turbines exhibits
bird or bat collision fatality higher
than predicted, Tier 5 studies may
be useful in evaluating alternative
mitigation measures at that
turbine/turbine string.
• There is the potential for
significant fatality impacts or
significant adverse impacts to
habitat for species of concern,
there is a need to assess the
impacts more closely, and there
is uncertainty over how these
impacts will be mitigated.
• Fatality and/or significant adverse
habitat impacts suggest the
potential for a reduction in the
viability of an affected population,
in which case studies on the
potential for population impacts
may be warranted.
• A developer evaluates the
effectiveness of a risk reduction
measure before deciding to
continue the measure permanently
or whether to use the measure
when implementing future phases
of a project.
In the event additional turbines
are proposed as an expansion of
an existing project, results from
Tier 4 and Tier 5 studies and
the decision-making framework
contained in the tiered approach
can be used to determine
whether the project should be
expanded and whether additional
information should be collected. It
may also be necessary to evaluate
whether additional measures are
warranted to reduce significant
adverse impacts to species.

Tier 5 Study Design Considerations
As discussed in Chapter 4 Tier 3,
Tier 5 studies will be highly variable
44 

and unique to the circumstances of
the individual project, and therefore
these Guidelines do not provide
specific guidance on all potential
approaches, but make some general
statements about study design.
Specific Tier 5 study designs will
depend on the types of questions,
the specific project, and practical
considerations. The most common
practical considerations include the
area being studied, the time period
of interest, the species of concern,
potentially confounding variables,
time available to conduct studies,
project budget, and the magnitude
of the anticipated impacts. When
possible it is usually desirable to
collect data before construction to
address Tier 5 questions. Design
considerations for these studies are
including in Tier 3.
One study design is based on
an experimental approach to
evaluating mitigation measures,
where the project proponent
will generally select several
alternative management
approaches to design, implement,
and test. The alternatives are
generally incorporated into sound
experimental designs. Monitoring
and evaluation of each alternative
helps the developer to decide which
alternative is more effective in
meeting objectives, and informs
adjustments to the next round of
management decisions. The need
for this type of study design can be
best determined by communication
between the project operator, the
Service field office, and the state
wildlife agency, on a project-byproject basis. This study design
requires developers and operators
to identify strategies to adjust
management and/or mitigation
measures if monitoring indicates
that anticipated impacts are being
exceeded. Such strategies should
include a timeline for periodic
reviews and adjustments as well
as a mechanism to consider and
implement additional mitigation
measures as necessary after the
project is developed.
When pre-construction data are
unavailable and/or a suitable
reference area is lacking, the
reference Control Impact Design

(Morrison et al. 2008) is the
recommended design. The lack of
a suitable reference area also can
be addressed using the Impact
Gradient Design, when habitat
and species use are homogenous
in the assessment area prior to
development. When applied both
pre- and post-construction, the
Impact Gradient Design is a suitable
replacement for the classic BACI
(Morrison et al. 2008).
In the study of habitat impacts, the
resource selection function (RSF)
study design (see Anderson et al
1999; Morrison et al. 2008; Manly
et al. 2002) is a statistically robust
design, either with or without
pre-construction and reference
data. Habitat selection is modeled
as a function of characteristics
measured on resource units and the
use of those units by the animals
of interest. The RSF allows the
estimation of the probability of
use as a function of the distance to
various environmental features,
including wind energy facilities, and
thus provides a direct quantification
of the magnitude of the displacement
effect. RSF could be improved with
pre-construction and reference area
data. Nevertheless, it is a relatively
powerful approach to documenting
displacement or the effect of
mitigation measures designed to
reduce displacement even without
those additional data.
Tier 5 Examples
As described earlier, Tier 5
studies will not be conducted at
most projects, and the specific
Tier 5 questions and methods for
addressing these questions will
depend on the individual project
and the concerns raised during
pre-construction studies and
during operational phases. Rather
than provide specific guidance on
all potential approaches, these
Guidelines offer the following case
studies as examples of studies that
have attempted to answer Tier 5
questions.
Habitat impacts - displacement and
demographic impact studies

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
gradient. RSF and impact gradient
designs may not require specialized
data gathering during Tier 3.

Rows of wind turbines. Credit: Joshua Winchell, USFWS

Studies to assess impacts may
include quantifying species’ habitat
loss (e.g., acres of lost grassland
habitat for grassland songbirds)
and habitat modification. For
example, an increase in edge may
result in greater nest parasitism
and nest predation. Assessing
indirect impacts may include two
important components: 1) indirect
effects on wildlife resulting from
displacement, due to disturbance,
habitat fragmentation, loss, and
alteration; and 2) demographic
effects that may occur at the
local, regional or population-wide
levels due to reduced nesting and
breeding densities, increased
isolation between habitat patches,
and effects on behavior (e.g., stress,
interruption, and modification).
These factors can individually
or cumulatively affect wildlife,
although some species may be able
to habituate to some or perhaps all
habitat changes. Indirect impacts
may be difficult to quantify but
their effects may be significant (e.g.,
Stewart et al. 2007, Pearce-Higgins
et al. 2008, Bright et al. 2008,
Drewitt and Langston 2006, Robel et
al. 2004, Pruett et al. 2009).
Example: in southwestern
Pennsylvania, development of a
project is proceeding at a site located

within the range of a state-listed
terrestrial species. Surveys were
performed at habitat locations
appropriate for use by the animal,
including at control sites. Postconstruction studies are planned
at all locations to demonstrate any
displacement effects resulting from
the construction and operation of the
project.
The Service recognizes that
indirect impact studies may not
be appropriate for most individual
projects. Consideration should be
given to developing collaborative
research efforts with industry,
government agencies, and NGOs to
conduct studies to address indirect
impacts.
Indirect impacts are considered
potentially significant adverse
threats to species such as prairie
grouse (prairie chickens, sharptailed grouse), and sage grouse,
and demographic studies may be
necessary to determine the extent
of these impacts and the need for
mitigation.
Displacement studies may use any
of the study designs describe earlier.
The most scientifically robust study
designs to estimate displacement
effects are BACI, RSF, and impact

Telemetry studies that measure
impacts of the project development
on displacement, nesting, nest
success, and survival of prairie
grouse and sage grouse in different
environments (e.g., tall grass,
mixed grass, sandsage, sagebrush)
will require spatial and temporal
replication, undisturbed reference
sites, and large sample sizes
covering large areas. Examples
of study designs and analyses
used in the studies of other
forms of energy development are
presented in Holloran et al. (2005),
Pitman et al. (2005), Robel et al.
(2004), and Hagen et al. (2011).
Anderson et al. (1999) provides a
thorough discussion of the design,
implementation, and analysis
of these kinds of field studies
and should be consulted when
designing the BACI study.
Studies are being initiated to
evaluate effects of wind energy
development on greater sage
grouse in Wyoming. In addition to
measuring demographic patterns,
these studies will use the RSF
study design (see Sawyer et al.
2006) to estimate the probability of
sage grouse use as a function of the
distance to environmental features,
including an existing and a proposed
project.
In certain situations, such as for
a proposed project site that is
relatively small and in a more or
less homogeneous landscape, an
impact gradient design may be
an appropriate means to assess
avoidance of the wind energy facility
by resident populations (Strickland
et al., 2002). For example, Leddy
et al. 1999 used the impact gradient
design to evaluate grassland bird
density as a function of the distance
from wind turbines. Data were
collected at various distances from
turbines along transects.
This approach provides information
on whether there is an effect,
and may allow quantification of
the gradient of the effect and the
distance at which the displacement
  45

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
effect no longer exists – the
assumption being that the data
collected at distances beyond
the influence of turbines are the
reference data (Erickson et al.,
2007). An impact gradient analysis
could also involve measuring the
number of breeding grassland birds
counted at point count plots as a
function of distance from the wind
turbines (Johnson et al. 2000).
Sound and Wildlife
Turbine blades at normal operating
speeds can generate levels of sound
beyond ambient background levels.
Construction and maintenance
activities can also contribute
to sound levels by affecting
communication distance, an animal’s
ability to detect calls or danger,
or to forage. Sound associated
with developments can also cause
behavioral and/or physiological
effects, damage to hearing from
acoustic over-exposure, and masking
of communication signals and other
biologically relevant sounds (Dooling
and Popper 2007). Some birds are
able to shift their vocalizations to
reduce the masking effects of noise.
However, when shifts don’t occur
or are insignificant, masking may
prove detrimental to the health and
survival of wildlife (Barber et al.
2010). Data suggest noise increases
of 3 dB to 10 dB correspond to 30
percent to 90 percent reductions
in alerting distances for wildlife,
respectively (Barber et al. 2010).
The National Park Service has
been investigating potential
impacts to wildlife due to
alterations in sound level and
type. However, further research
is needed to better understand
this potential impact. Research
may include: how wind facilities
affect background sound levels;
whether masking, disturbance, and
acoustical fragmentation occur;
and how turbine, construction, and
maintenance sound levels can vary
by topographic area.
Levels of fatality beyond those
predicted
More intensive post-construction
fatality studies may be used to
46 

determine relationships between
fatalities and weather, wind speed
or other covariates, which usually
require daily carcass searches.
Fatalities determined to have
occurred the previous night can
be correlated with that night’s
weather or turbine characteristics
to establish important relationships
that can then be used to evaluate the
most effective times and conditions
to implement measures to reduce
collision fatality at the project.
Measures to address fatalities
The efficacy of operational changes
(e.g. changing turbine cut-in speed)
of a project to reduce collision
fatalities has only recently been
evaluated (Arnett et al. 2009,
Baerwald et al 2009). Operational
changes to address fatalities should
be applied only at sites where
collision fatalities are predicted or
demonstrated to have significant
adverse impacts.
Tier 5 Studies and Research
The Service makes a distinction
between Tier 5 studies focused
on project-specific impacts and
research (which is discussed earlier
in the Guidelines). For example,
developers may be encouraged to
participate in collaborative studies
(see earlier discussion of Research)
or asked to conduct a study on an
experimental mitigation technique,
such as differences in turbine cut-in
speed to reduce bat fatalities. Such
techniques may show promise in
mitigating the impacts of wind
energy development to wildlife,
but their broad applicability for
mitigation purposes has not been
demonstrated. Such techniques
should not be routinely applied
to projects, but application at
appropriate sites will contribute to
the breadth of knowledge regarding
the efficacy of such measures in
addressing collision fatalities. In
addition, studies involving multiple
sites and academic researchers
can provide more robust research
results, and such studies take
more time and resources than are
appropriately carried out by one
developer at a single site. Examples
below demonstrate collaborative

research efforts to address
displacement, operational changes,
and population level impacts.
Studies of Indirect Effects
The Service provides two examples
below of ongoing studies to assess
the effects of indirect impacts
related to wind energy facilities.
Kansas State University, as part
of the NWCC Grassland Shrubsteppe Species Collaborative, is
undertaking a multi-year research
project to assess the effects of wind
energy facilities on populations of
greater prairie-chickens (GPCH) in
Kansas. Initially the research was
based on a Before/After Control/
Impact (BACI) experimental design
involving three replicated study
sites in the Flint Hills and Smoky
Hills of eastern Kansas. Each
study site consisted of an impact
area where a wind energy facility
was proposed to be developed and a
nearby reference area with similar
rangeland characteristics where
no development was planned. The
research project is a coordinated
field/laboratory effort, i.e., collecting
telemetry and observational data
from adult and juvenile GPCH in the
field, and determining population
genetic attributes of GPCH in the
laboratory from blood samples of
birds and the impact and reference
areas. Detailed data on GPCH
movements, demography, and
population genetics were gathered
from all three sites from 2007 to
2010. By late 2008, only one of the
proposed wind energy facilities was
developed (the Meridian Way Wind
Farm in the Smoky Hills of Cloud
County), and on-going research
efforts are focused on that site.
The revised BACI study design
now will produce two years of preconstruction data (2007 and 2008),
and three years of post-construction
data (2009, 2010, and 2011) from
a single wind energy facility site
(impact area) and its reference
area. Several hypotheses were
formulated for testing to determine
if wind energy facilities impacted
GPCH populations, including but not
limited to addressing issues relating
to: lek attendance, avoidance of
turbines and associated features,

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
nest success and chick survival,
habitat usage, adult mortality
and survival, breeding behavior,
and natal dispersal. A myriad of
additional significant avenues are
being pursued as a result of the rich
database that has been developed
for the GPCH during this research
effort. GPCH reproductive data will
be collected through the summer of
2011 whereas collection of data from
transmitter-equipped GPCH will
extend through the lekking season
of 2012 to allow estimates of survival
of GPCH over the 2011-2012 winter.
At the conclusion of the study, the
two years of pre-construction data
and three years of post-construction
data will be analyzed and submitted
to peer-reviewed journals for
publication.
Erickson et al. (2004) evaluated
the displacement effect of a
large wind energy facility in the
Pacific Northwest. The study
was conducted in a relatively
homogeneous grassland landscape.
Erickson et al. (2004) conducted
surveys of breeding grassland
birds along 300 meter transects
perpendicular to strings of wind
turbines. Surveys were conducted
prior to construction and after
commercial operation. The basic
study design follows the Impact
Gradient Design (Morrison et
al. 2008) and in this application,
conformed to a special case of BACI
where areas at the distal end of each
transect were considered controls
(i.e., beyond the influence of the
turbines). In this study, there is
no attempt to census birds in the
area, and observations per survey
are used as an index of abundance.
Additionally, the impact-gradient
study design resulted in less effort
than a BACI design with offsite
control areas. Erickson et al. (2004)
found that grassland passerines
as a group, as well as grasshopper
sparrows and western meadowlarks,
showed reduced use in the first 50
meter segment nearest the turbine
string. About half of the area
within that segment, however, had
disturbed vegetation and separation
of behavior avoidance from physical
loss of habitat in this portion of the
area was impossible. Horned larks
and savannah sparrows appeared

unaffected. The impact gradient
design is best used when the
study area is relatively small and
homogeneous.
Operational Changes to Reduce
Collision Fatality
Arnett et al. (2009) conducted
studies on the effectiveness of
changing turbine cut-in speed
on reducing bat fatality at wind
turbines at the Casselman Wind
Project in Somerset County,
Pennsylvania. Their objectives were
to: 1) determine the difference
in bat fatalities at turbines with
different cut-in-speeds relative to
fully operational turbines; and 2)
determine the economic costs of the
experiment and estimated costs for
the entire area of interest under
different curtailment prescriptions
and timeframes. Arnett et al. (2009)
reported substantial reductions in
bat fatalities with relatively modest
power losses.
In Kenedy County, Texas,
investigators are refining and testing
a real-time curtailment protocol.
The projects use an avian profiling
radar system to detect approaching
“flying vertebrates” (birds and
bats), primarily during spring and
fall bird and bat migrations. The
blades automatically idle when risk
reaches a certain level and weather
conditions are particularly risky.
Based on estimates of the number
and timing of migrating raptors,
feathering (real-time curtailment)
experiments are underway in
Tehuantepec, Mexico, where raptor
migration through a mountain pass
is extensive.
Other tools, such as thermal
imaging (Horn et al. 2008) or
acoustic detectors (Kunz et al.
2007), have been used to quantify
post-construction bat activity in
relation to weather and turbine
characteristics for improving
operational change efforts. For
example, at the Mountaineer
project in 2003, Tier 4 studies
(weekly searches at every turbine)
demonstrated unanticipated and
high levels of bat fatalities (Kerns
and Kerlinger 2004). Daily searches
were instituted in 2004 and revealed

that fatalities were strongly
associated with low-averagewind-speed nights, thus providing
a basis for testing operational
changes (Arnett 2005, Arnett et al.
2008). The program also included
behavioral observations using
thermal imaging that demonstrated
higher bat activity at lower wind
speeds (Horn et al. 2008).
Studies are currently underway to
design and test the efficacy of an
acoustic deterrent device to reduce
bat fatalities at wind facilities
(E.B. Arnett, Bat Conservation
International, under the auspices
of BWEC). Prototypes of the
device have been tested in the
laboratory and in the field with some
success. Spanjer (2006) tested the
response of big brown bats to a
prototype eight speaker deterrent
emitting broadband white noise at
frequencies from 12.5–112.5 kHz
and found that during non-feeding
trials, bats landed in the quadrant
containing the device significantly
less when it was broadcasting
broadband noise. Spanjer (2006)
also reported that during feeding
trials, bats never successfully
took a tethered mealworm when
the device broadcast sound, but
captured mealworms near the
device in about 1/3 of trials when it
was silent. Szewczak and Arnett
(2006, 2007) tested the same acoustic
deterrent in the field and found that
when placed by the edge of a small
pond where nightly bat activity
was consistent, activity dropped
significantly on nights when the
deterrent was activated. Horn et
al. (2007) tested the effectiveness of
a larger, more powerful version of
this deterrent device on reducing
nightly bat activity and found mixed
results. In 2009, a new prototype
device was developed and tested
at a project in Pennsylvania. Ten
turbines were fitted with deterrent
devices, daily fatality searches were
conducted, and fatality estimates
were compared with those from
15 turbines without deterrents
(i.e., controls) to determine if
bat fatalities were reduced. This
experiment found that estimated
bat fatalities per turbine were 20
to 53 percent lower at treatment
turbines compared to controls.
  47

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
More experimentation is required.
At the present time, there is not
an operational deterrent available
that has demonstrated effective
reductions in bat kills (E. B. Arnett,
Bat Conservation International,
unpublished data).
Assessment of Population-level
Impacts
The Altamont Pass Wind Resource
Area (APWRA) has been the subject
of intensive scrutiny because of avian
fatalities, especially for raptors, in
an area encompassing more than
5,000 wind turbines (e.g., Orloff
and Flannery 1992; Smallwood
and Thelander 2004, 2005). Field
studies on golden eagles, a longlived raptor species, have been
completed using radio telemetry at
APWRA to understand population
demographics, assess impacts from
wind turbines, and explore measures
to effectively reduce the incidence of
golden eagle mortality for this area.
(Hunt et al. 1999, and Hunt 2002).
Results from nesting surveys (Hunt
2002) indicated that there was no
decline in eagle territory occupancy.
However Hunt (2002) also found that
subadult and floater components of
golden eagle populations at APWRA
are highly vulnerable to wind turbine
mortality and results from this
study indicate that turbine mortality
prevented the maintenance of
substantial reserves of nonbreeding
adults characteristic of healthy
populations elsewhere, suggesting
the possibility of an eventual decline
in the breeding population (Hunt
and Hunt 2006). Hunt conducted
follow-up surveys in 2005 (Hunt and
Hunt 2006) and determined that all
58 territories occupied by eagle pairs
in 2000 were occupied in 2005. It
should be noted however that golden
eagle studies at APWRA (Hunt et
al. 1999, Hunt 2002, and Hunt and
Hunt 2006) were all conducted after
the APWRA was constructed and
the species does not nest within
the footprint of the APWRA itself
(Figure 4; Hunt and Hunt 2006).
The APWRA is an area of about 160
sq. km (Hunt 2002) and presumably
golden eagles formerly nested within
this area. The loss of breeding eagle
pairs from the APWRA suggests
these birds have all been displaced
48 

Golden eagle. Credit: George Gentry, USFWS

by the project, or lost due to
various types of mortality including
collisions with turbine blades.

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 7: Best Management Practices
Site Construction and Operation
During site planning and
development, careful attention to
reducing risk of adverse impacts
to species of concern from wind
energy projects, through careful
site selection and facility design,
is recommended. The following
BMPs can assist a developer in the
planning process to reduce potential
impacts to species of concern. Use of
these BMPs should ensure that the
potentially adverse impacts to most
species of concern and their habitats
present at many project sites would
be reduced, although compensatory
mitigation may be appropriate at a
project level to address significant
site-specific concerns and preconstruction study results.
These BMPs will evolve over time
as additional experience, learning,
monitoring and research becomes
available on how to best minimize
wildlife and habitat impacts from
wind energy projects. Service
should work with the industry,
stakeholders and states to evaluate,
revise and update these BMPs on
a periodic basis, and the Service
should maintain a readily available
publication of recommended,
generally accepted best practices.
1. Minimize, to the extent
practicable, the area disturbed by
pre-construction site monitoring
and testing activities and
installations.
2. Avoid locating wind energy
facilities in areas identified as
having a demonstrated and
unmitigatable high risk to birds
and bats.
3. Use available data from state
and federal agencies, and other
sources (which could include
maps or databases), that show
the location of sensitive resources
and the results of Tier 2 and/or
3 studies to establish the layout

Wind electronic developers. Credit: NREL

of roads, power lines, fences, and
other infrastructure.
4. Minimize, to the maximum
extent practicable, roads,
power lines, fences, and other
infrastructure associated with a
wind development project. When
fencing is necessary, construction
should use wildlife compatible
design standards.
5. Use native species when seeding
or planting during restoration.
Consult with appropriate state
and federal agencies regarding
native species to use for
restoration.
6. To reduce avian collisions,
place low and medium voltage
connecting power lines
associated with the wind energy
development underground to
the extent possible, unless burial
of the lines is prohibitively
expensive (e.g., where shallow
bedrock exists) or where greater
adverse impacts to biological
resources would result:
a. Overhead lines may be
acceptable if sited away

from high bird crossing
locations, to the extent
practicable, such as between
roosting and feeding areas or
between lakes, rivers, prairie
grouse and sage grouse leks,
and nesting habitats. To
the extent practicable, the
lines should be marked in
accordance with Avian Power
Line Interaction Committee
(APLIC) collision guidelines.
b. Overhead lines may be used
when the lines parallel tree
lines, employ bird flight
diverters, or are otherwise
screened so that collision
risk is reduced.
c. Above-ground low and
medium voltage lines,
transformers and conductors
should follow the 2006
or most recent APLIC
“Suggested Practices for
Avian Protection on Power
Lines.”
7. Avoid guyed communication
towers and permanent met
towers at wind energy project
sites. If guy wires are necessary,
  49

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
bird flight diverters or high
visibility marking devices should
be used.
8. Where permanent meteorological
towers must be maintained on
a project site, use the minimum
number necessary.
9. Use construction and
management practices to
minimize activities that may
attract prey and predators to the
wind energy facility.
10. Employ only red, or dual red
and white strobe, strobe-like,
or flashing lights, not steady
burning lights, to meet Federal
Aviation Administration (FAA)
requirements for visibility
lighting of wind turbines,
permanent met towers, and
communication towers. Only a
portion of the turbines within the
wind project should be lighted,
and all pilot warning lights
should fire synchronously.
11. Keep lighting at both operation
and maintenance facilities and
substations located within half
a mile of the turbines to the
minimum required:
a. Use lights with motion or
heat sensors and switches
to keep lights off when not
required.
b. Lights should be hooded
downward and directed to
minimize horizontal and
skyward illumination.
c. Minimize use of highintensity lighting,
steady-burning, or bright
lights such as sodium vapor,
quartz, halogen, or other
bright spotlights.
d. All internal turbine nacelle
and tower lighting should
be extinguished when
unoccupied.
12. Establish non-disturbance
buffer zones to protect sensitive
habitats or areas of high risk
for species of concern identified
in pre-construction studies.
50 

Determine the extent of the
buffer zone in consultation with
the Service and state, local and
tribal wildlife biologists, and land
management agencies (e.g., U.S.
Bureau of Land Management
(BLM) and U.S. Forest Service
(USFS)), or other credible
experts as appropriate.
13. Locate turbines to avoid
separating bird and bat species
of concern from their daily
roosting, feeding, or nesting sites
if documented that the turbines’
presence poses a risk to species.
14. Avoid impacts to hydrology and
stream morphology, especially
where federal or state-listed
aquatic or riparian species may
be involved. Use appropriate
erosion control measures in
construction and operation to
eliminate or minimize runoff into
water bodies.
15. When practical use tubular
towers or best available
technology to reduce ability of
birds to perch and to reduce risk
of collision.
16. After project construction,
close roads not needed for site
operations and restore these
roadbeds to native vegetation,
consistent with landowner
agreements.
17. Minimize the number and length
of access roads; use existing
roads when feasible.
18. Minimize impacts to wetlands
and water resources by following
all applicable provisions of
the Clean Water Act (33 USC
1251-1387) and the Rivers and
Harbors Act (33 USC 301 et
seq.); for instance, by developing
and implementing a storm water
management plan and taking
measures to reduce erosion and
avoid delivery of road-generated
sediment into streams and
waters.
19. Reduce vehicle collision risk to
wildlife by instructing project
personnel to drive at appropriate
speeds, be alert for wildlife, and

use additional caution in low
visibility conditions.
20. Instruct employees, contractors,
and site visitors to avoid
harassing or disturbing wildlife,
particularly during reproductive
seasons.
21. Reduce fire hazard from vehicles
and human activities (instruct
employees to use spark arrestors
on power equipment, ensure
that no metal parts are dragging
from vehicles, use caution with
open flame, cigarettes, etc.).
Site development and operation
plans should specifically address
the risk of wildfire and provide
appropriate cautions and
measures to be taken in the event
of a wildfire.
22. Follow federal and state
measures for handling toxic
substances to minimize danger to
water and wildlife resources from
spills. Facility operators should
maintain Hazardous Materials
Spill Kits on site and train
personnel in the use of these.
23. Reduce the introduction and
spread of invasive species by
following applicable local policies
for invasive species prevention,
containment, and control, such as
cleaning vehicles and equipment
arriving from areas with known
invasive species issues, using
locally sourced topsoil, and
monitoring for and rapidly
removing invasive species at least
annually.
24. Use invasive species prevention
and control measures as specified
by county or state requirements,
or by applicable federal agency
requirements (such as Integrated
Pest Management) when federal
policies apply.
25. Properly manage garbage
and waste disposal on project
sites to avoid creating
attractive nuisances for
wildlife by providing them with
supplemental food.
26. Promptly remove large animal
carcasses (e.g., big game,

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
domestic livestock, or feral
animal).
27. Wildlife habitat enhancements
or improvements such as ponds,
guzzlers, rock or brush piles
for small mammals, bird nest
boxes, nesting platforms, wildlife
food plots, etc. should not be
created or added to wind energy
facilities. These wildlife habitat
enhancements are often desirable
but when added to a wind energy
facility result in increased
wildlife use of the facility which
may result in increased levels of
injury or mortality to them.

Retrofitting, Repowering, and
Decommissioning
As with project construction,
these Guidelines offer BMPs for
the retrofitting, repowering, and
decommissioning phases of wind
energy projects.
Retrofitting
Retrofitting is defined as replacing
portions of existing wind turbines
or project facilities so that at
least part of the original turbine,
tower, electrical infrastructure
or foundation is being utilized.
Retrofitting BMPs include:
1. Retrofitting of turbines should
use installation techniques that
minimize new site disturbance,
soil erosion, and removal of
vegetation of habitat value.
2. Retrofits should employ shielded,
separated or insulated electrical
conductors that minimize
electrocution risk to avian wildlife
per APLIC (2006).
3. Retrofit designs should prevent
nests or bird perches from being
established in or on the wind
turbine or tower.
4. FAA visibility lighting of wind
turbines should employ only red,
or dual red and white strobe,
strobe-like, or flashing lights, not
steady burning lights.
5. Lighting at both operation
and maintenance facilities and

substations located within half
a mile of the turbines should be
kept to the minimum required:
a. Use lights with motion or heat
sensors and switches to keep
lights off when not required.
b. Lights should be hooded
downward and directed to
minimize horizontal and
skyward illumination.
c. Minimize use of high intensity
lighting, steady-burning, or
bright lights such as sodium
vapor, quartz, halogen, or
other bright spotlights.
6. Remove wind turbines when they
are no longer cost effective to
retrofit.
Repowering
Repowering may include removal
and replacement of turbines and
associated infrastructure. BMPs
include:
1. To the greatest extent
practicable, existing roads,
disturbed areas and turbine
strings should be re-used in
repower layouts.
2. Roads and facilities that are
no longer needed should be
demolished, removed, and their
footprint stabilized and re-seeded
with native plants appropriate for
the soil conditions and adjacent
habitat and of local seed sources
where feasible, per landowner
requirements and commitments.

5. Above-ground low and medium
voltage lines, transformers and
conductors should follow the
2006 or most recent APLIC
“Suggested Practices for Avian
Protection on Power Lines.”
6. Guyed structures should be
avoided. If use of guy wires
is absolutely necessary, they
should be treated with bird
flight diverters or high visibility
marking devices, or are located
where known low bird use will
occur.
7. FAA visibility lighting of wind
turbines should employ only red,
or dual red and white strobe,
strobe-like, or flashing lights, not
steady burning lights.
8. Lighting at both operation
and maintenance facilities and
substations located within ½ mile
of the turbines should be kept to
the minimum required.
a. Use lights with motion or heat
sensors and switches to keep
lights off when not required.
b. Lights should be hooded
downward and directed to
minimize horizontal and
skyward illumination.

3. Existing substations and
ancillary facilities should be
re-used in repowering projects to
the extent practicable.
4. Existing overhead lines may be
acceptable if located away from
high bird crossing locations, such
as between roosting and feeding
areas, or between lakes, rivers
and nesting areas. Overhead
lines may be used when they
parallel tree lines, employ bird
flight diverters, or are otherwise
screened so that collision risk is
reduced.

Towers are being lifted as work continues on the 2
MW Gamesa wind turbine that is being installed at
the NWTC . Credit: NREL

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
c. Minimize use of high intensity
lighting, steady-burning, or
bright lights such as sodium
vapor, quartz, halogen, or
other bright spotlights.
Decommissioning
Decommissioning is the cessation
of wind energy operations and
removal of all associated equipment,
roads, and other infrastructure.
The land is then used for another
activity. During decommissioning,
contractors and facility operators
should apply BMPs for road grading
and native plant re-establishment
to ensure that erosion and overland
flows are managed to restore preconstruction landscape conditions.
The facility operator, in conjunction
with the landowner and state and
federal wildlife agencies, should
restore the natural hydrology and
plant community to the greatest
extent practical.
1. Decommissioning methods should
minimize new site disturbance and
removal of native vegetation, to
the greatest extent practicable.
2. Foundations should be removed
to a minimum of three feet below
surrounding grade, and covered
with soil to allow adequate root
penetration for native plants, and
so that subsurface structures do
not substantially disrupt ground
water movements. Three feet is
typically adequate for agricultural
lands.
3. If topsoils are removed during
decommissioning, they should
be stockpiled and used as topsoil
when restoring plant communities.
Once decommissioning activity
is complete, topsoils should be
restored to assist in establishing
and maintaining pre-construction
native plant communities to the
extent possible, consistent with
landowner objectives.
4. Soil should be stabilized and
re-vegetated with native plants
appropriate for the soil conditions
and adjacent habitat, and of local
seed sources where feasible,
consistent with landowner
objectives.
52 

5. Surface water flows should be
restored to pre-disturbance
conditions, including removal
of stream crossings, roads, and
pads, consistent with storm water
management objectives and
requirements.
6. Surveys should be conducted
by qualified experts to detect
populations of invasive species,
and comprehensive approaches
to preventing and controlling
invasive species should be
implemented and maintained as
long as necessary.
7. Overhead pole lines that are no
longer needed should be removed.
8. After decommissioning, erosion
control measures should be
installed in all disturbance areas
where potential for erosion exists,
consistent with storm water
management objectives and
requirements.
9. Fencing should be removed unless
the landowner will be utilizing the
fence.
10. Petroleum product leaks and
chemical releases should be
remediated prior to completion of
decommissioning.

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 8: Mitigation
Mitigation is defined in this
document as avoiding or minimizing
significant adverse impacts, and
when appropriate, compensating
for unavoidable significant adverse
impacts, as determined through
the tiered approach described in
the recommended Guidelines. The
Service places emphasis in project
planning on first avoiding, then
minimizing, potential adverse
impacts to wildlife and their habitats.
Several tools are available to
determine appropriate mitigation,
including the Service Mitigation
Policy (USFWS Mitigation Policy,
46 FR 7656 (1981)). The Service
policy provides a common basis
for determining how and when to
use different mitigation strategies,
and facilitates earlier consideration
of wildlife values in wind energy
project planning.

additional mitigation for those
adverse effects from operations may
need to be implemented.

Under the Service Mitigation Policy,
the highest priority is for mitigation
to occur on-site within the project
planning area. The secondary
priority is for the mitigation to
occur off-site. Off-site mitigation
should first occur in proximity to
the planning area within the same
ecological region and secondarily
elsewhere within the same ecological
region. Generally, the Service
prefers on-site mitigation over offsite mitigation because this approach
most directly addresses project
impacts at the location where they
actually occur. However, there may
be individual cases where off-site
mitigation could result in greater
net benefits to affected species
and habitats. Developers should
work with the Service in comparing
benefits among multiple alternatives.

CEQ issued guidance in February
2011 on compliance with the
National Environmental Policy Act
(NEPA) entitled, “Appropriate Use
of Mitigation and Monitoring and
Clarifying the Appropriate Use of

In some cases, a project’s effects
cannot be forecast with precision.
The developer and the agencies may
be unable to make some mitigation
decisions until post-construction
data have been collected. If
significant adverse effects have
not been adequately addressed,

Mitigation measures implemented
post-construction, whether in
addition to those implemented preconstruction or whether they are
new, are appropriate elements of
the tiered approach. The general
terms and funding commitments for
future mitigation and the triggers
or thresholds for implementing such
compensation should be developed at
the earliest possible stage in project
development. Any mitigation
implemented after a project is
operational should be well defined,
bounded, technically feasible, and
commensurate with the project
effects.

NEPA Guidance on Mitigation

Mitigated Findings of No Significant
Impact.” This new guidance clarifies
that when agencies premise their
Finding of No Significant Impact
on a commitment to mitigate the
environmental impacts of a proposed
action, they should adhere to those
commitments, publicly report on
those efforts, monitor how they
are implemented, and monitor the
effectiveness of the mitigation.
To the extent that a federal nexus
with a wind project exists, for
example, developing a project on
federal lands or obtaining a federal
permit, the lead federal action
agency should make its decision
based in part on a developer’s
commitment to mitigate adverse
environmental impacts. The federal
action agency should ensure that
the developer adheres to those
commitments, monitors how they
are implemented, and monitors
the effectiveness of the mitigation.
Additionally, the lead federal action
agency should make information
on mitigation monitoring available
to the public through its web site;

Greater prairie chicken. Credit: Amy Thornburg, USFWS

  53

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
and should ensure that mitigation
successfully achieves its goals.

Compensatory Mitigation
Compensatory mitigation as
defined in this document refers to
replacement of project-induced
losses to fish and wildlife resources.
Substitution or offsetting of fish
and wildlife resource losses with
resources considered to be of
equivalent biological value.
- In-kind – Providing or
managing substitute resources
to replace the value of the
resources lost, where such
substitute resources are
physically and biologically the
same or closely approximate to
those lost.
- Out-of-kind – Providing or
managing substitute resources
to replace the value of the
resources lost, where such
substitute resources are
physically or biologically
different from those lost. This
may include conservation or
mitigation banking, research or
other options.
The amount of compensation,
if necessary, will depend on the
effectiveness of any avoidance and
minimization measures undertaken.
If a proposed wind development
is poorly sited with regard to
wildlife effects, the most important
mitigation opportunity is largely lost
and the remaining options can be
expensive, with substantially greater
environmental effects.
Compensation is most often
appropriate for habitat loss under
limited circumstances or for direct
take of wildlife (e.g., Habitat
Conservation Plans). Compensatory
mitigation may involve contributing
to a fund to protect habitat or
otherwise support efforts to reduce
existing impacts to species affected
by a wind project. Developers
should communicate with the Service
and state agency prior to initiating
such an approach.
Ideally, project impact assessment
is a cooperative effort involving
54 

the developer, the Service, tribes,
local authorities, and state resource
agencies. The Service does not
expect developers to provide
compensation for the same habitat
loss more than once. But the
Service, state resource agencies,
tribes, local authorities, state and
federal land management agencies
may have different species or
habitats of concern, according to
their responsibilities and statutory
authorities. Hence, one entity may
seek mitigation for a different group
of species or habitat than does
another.

Migratory Birds and Eagles
Some industries, such as the electric
utilities, have developed operational
and deterrent measures that
when properly used can avoid or
minimize “take” of migratory birds.
Many of these measures to avoid
collision and electrocution have been
scientifically tested with publication
in peer-reviewed, scientific journals.
The Service encourages the wind
industry to use these measures
in siting, placing, and operating
all power lines, including their
distribution and grid-connecting
transmission lines.

has additional information on the use
of compensation for programmatic
permits.

Endangered Species
The ESA has provisions that
allow for compensation through
the issuance of an Incidental
Take Permit (ITP). Under the
ESA, mitigation measures are
determined on a case by case basis,
and are based on the needs of the
species and the types of effects
anticipated. If a federal nexus
exists, or if a developer chooses to
seek an ITP under the ESA, then
effects to listed species need to be
evaluated through the Section 7 and/
or Section 10 processes. If an ITP
is requested, it and the associated
HCP must provide for minimization
and mitigation to the maximum
extent practicable, in addition to
meeting other necessary criteria
for permit issuance. For further
information about compensation
under federal laws administered
by the Service, see the Service’s
Habitat and Resource Conservation
website http://www.fws.gov/
habitatconservation.

E.O. 13186, which addresses
responsibilities of federal agencies
to protect migratory birds, includes
a directive to federal agencies to
restore and enhance the habitat
of migratory birds as practicable.
E.O. 13186 provides a basis and a
rationale for compensating for the
loss of migratory bird habitat that
results from developing wind energy
projects that have a federal nexus.
Regulations concerning eagle
take permits in 50 CFR 22.26
and 50 CFR 22.27 may allow for
compensation as part of permit
issuance. Compensation may be a
condition of permit issuance in cases
of nest removal, disturbance or
take resulting in mortality that will
likely occur over several seasons,
result in permanent abandonment
of one or more breeding territories,
have large scale impacts, occur at
multiple locations, or otherwise
contribute to cumulative negative
effects. The draft ECP Guidance

Bald eagle. Credit: USFWS

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Chapter 9: Advancing Use, Cooperation and
Effective Implementation
This chapter discusses a variety
of policies and procedures that
may affect the way wind project
developers and the Service work
with each other as well as with state
and tribal governments and nongovernmental organizations. The
Service recommends that wind
project developers work closely
with field office staff for further
elaboration of these policies and
procedures.

Conflict Resolution
The Service and developers should
attempt to resolve any issues arising
from use of the Guidelines at the
Field Office level. Deliberations
should be in the context of the intent
of the Guidelines and be based on the
site-specific conditions and the best
available data. However, if there

is an issue that cannot be resolved
within a timely manner at the field
level, the developer and Service
staff will coordinate to bring the
matter up the chain of command in a
stepwise manner.

Bird and Bat Conservation Strategies
(BBCS)
The Service has recommended
that developers prepare written
records of their actions to avoid,
minimize and compensate for
potential adverse impacts. In the
past, the Service has referred to
these as Avian and Bat Protection
Plans (ABPP). However, ABPPs
have more recently been used for
transmission projects and less for
other types of development. For this
reason the Service is introducing
a distinct concept for wind energy

projects and calling them Bird
and Bat Conservation Strategies
(BBCS).
Typically, a project-specific BBCS
will explain the analyses, studies,
and reasoning that support
progressing from one tier to the
next in the tiered approach. A
wind energy project-specific BBCS
is an example of a document or
compilation of documents that
describes the steps a developer
could or has taken to apply these
Guidelines to mitigate for adverse
impacts and address the postconstruction monitoring efforts the
developer intends to undertake. A
developer may prepare a BBCS in
stages, over time, as analysis and
studies are undertaken for each
tier. It will also address the postconstruction monitoring efforts for
mortality and habitat effects, and
may use many of the components
suggested in the Suggested
Practices for Avian Protection on
Power Lines (APLIC 2006). Any
Service review of, or discussion
with a developer, concerning its
BBCS is advisory only, does not
result in approval or disapproval
of the BBCS by the Service, and
does not constitute a federal agency
action subject to the National
Environmental Policy Act or other
federal law applicable to such an
action.

Project Interconnection Lines

Electricity towers and wind turbines. Credit: NREL

The Guidelines are designed to
address all elements of a wind
energy facility, including the
turbine string or array, access
roads, ancillary buildings, and the
above- and below-ground electrical
lines which connect a project to the
transmission system. The Service
recommends that the project
evaluation include consideration
of the wildlife- and habitat-related
impacts of these electrical lines, and
that the developer include measures
to reduce impacts of these lines, such
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
as those outlined in the Suggested
Practices for Avian Protection on
Power Lines (APLIC 2006). The
Guidelines are not designed to
address transmission beyond the
point of interconnection to the
transmission system. The national
grid and proposed smart grid system
are beyond the scope of these
Guidelines.

Confidentiality of Site Evaluation
Process as Appropriate
Some aspects of the initial preconstruction risk assessment,
including preliminary screening and
site characterization, occur early
in the development process, when
land or other competitive issues
limit developers’ willingness to
share information on projects with
the public and competitors. Any
consultation or coordination with
agencies at this stage may include
confidentiality agreements.

Collaborative Research
Much uncertainty remains about
predicting risk and estimating
impacts of wind energy development
on wildlife. Thus there is a need
for additional research to improve
scientifically based decision-making
when siting wind energy facilities,
evaluating impacts on wildlife and
habitats, and testing the efficacy
of mitigation measures. More
extensive studies are needed to
further elucidate patterns and test
hypotheses regarding possible
solutions to wildlife and wind energy
impacts.
It is in the interests of wind
developers and wildlife agencies to
improve these assessments to better
mitigate the impacts of wind energy
development on wildlife and their
habitats. Research can provide data
on operational factors (e.g. wind
speed, weather conditions) that are
likely to result in fatalities. It could

9

www.batsandwind.org
www.nationalwind.org
11
www.nationalwind.org
12
http://www.awwi.org
13
http://www.energy.ca.gov/research
10

56 

also include studies of cumulative
impacts of multiple wind energy
projects, or comparisons of different
methods for assessing avian and bat
activity relevant to predicting risk.
Monitoring and research should be
designed and conducted to ensure
unbiased data collection that meets
technical standards such as those
used in peer review. Research
projects may occur at the same time
as project-specific Tier 4 and Tier 5
studies.
Research would usually result
from collaborative efforts involving
appropriate stakeholders, and is not
the sole or primary responsibility
of any developer. Research
partnerships (e.g., Bats and Wind
Energy Cooperative (BWEC)9,
Grassland and Shrub Steppe
Species Collaborative (GS3C)10 )
involving diverse players will be
helpful for generating common
goals and objectives and adequate
funding to conduct studies (Arnett
and Haufler 2003). The National
Wind Coordinating Collaborative
(NWCC)11 , the American Wind
Wildlife Institute (AWWI)12 , and
the California Energy Commission
(CEC)’s Public Interest Energy
Research Program13 all support
research in this area.
Study sites and access will be
necessary to design and implement
research, and developers are
encouraged to participate in these
research efforts when possible.
Subject to appropriations, the
Service also should fund priority
research and promote collaboration
and information sharing among
research efforts to advance science
on wind energy-wildlife interactions,
and to improve these Guidelines.

Service - State Coordination and
Cooperation
The Service encourages states to
increase compatibility between

state guidelines and these voluntary
Guidelines, protocols, data collection
methods, and recommendations
relating to wildlife and wind energy.
States that desire to adopt, or
those that have formally adopted,
wind energy siting, permitting, or
environmental review regulations
or guidelines are encouraged to
cooperate with the Service to
develop consistent state level
guidelines. The Service may be
available to confer, coordinate and
share its expertise with interested
states when a state lacks its own
guidance or program to address
wind energy-wildlife interactions.
The Service will also use states’
technical resources as much as
possible and as appropriate.
The Service will explore establishing
a voluntary state/federal program
to advance cooperation and
compatibility between the Service
and interested state and local
governments for coordinated review
of projects under both federal and
state wildlife laws. The Service,
and interested states, will consider
using the following tools to reach
agreements to foster consistency in
review of projects:
• Cooperation agreements with
interested state governments.
• Joint agency reviews to reduce
duplication and increase
coordination in project review.
• A communication mechanism:
• To share information about
prospective projects
• To coordinate project review
• To ensure that state and
federal regulatory processes,
and/or mitigation requirements
are being adequately
addressed

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
• To ensure that species of
concern and their habitats are
fully addressed
• Establishing consistent and
predictable joint protocols, data
collection methodologies, and
study requirements to satisfy
project review and permitting.
• Designating a Service
management contact within
each Regional Office to assist
Field Offices working with states
and local agencies to resolve
significant wildlife-related issues
that cannot be resolved at the
field level.
• Cooperative state/federal/
industry research agreements
relating to wind energy -wildlife
interactions.
Wind turbine in California.. Credit: NREL

The Service will explore
opportunities to:
• Provide training to states.
• Foster development of a national
geographic data base that
identifies development-sensitive
ecosystems and habitats.
• Support a national database for
reporting of mortality data on a
consistent basis.
• Establish national BMPs for wind
energy development projects.
• Develop recommended guidance
on study protocols, study
techniques, and measures
and metrics for use by all
jurisdictions.
• Assist in identifying and obtaining
funding for national research
priorities.

Service - Tribal Consultation and
Coordination
Federally-recognized Indian Tribes
enjoy a unique government-togovernment relationship with
the United States. The United
States Fish and Wildlife Service
(Service) recognizes Indian tribal
governments as the authoritative
voice regarding the management of

tribal lands and resources within the
framework of applicable laws. It is
important to recall that many tribal
traditional lands and tribal rights
extend beyond reservation lands.

the Tribe’s jurisdiction. Tribal
governments are encouraged to
strive for compatibility between
their guidelines and these
Guidelines.

The Service consults with Indian
tribal governments under the
authorities of Executive Order 13175
“Consultation and Coordination with
Indian Tribal Governments” and
supporting DOI and Service policies.
To this end, when it is determined
that federal actions and activities
may affect a Tribe’s resources
(including cultural resources), lands,
rights, or ability to provide services
to its members, the Service must,
to the extent practicable, seek to
engage the affected Tribe(s) in
consultation and coordination.

Tribal Wind Energy Development
on Lands that are not held in Trust

Tribal Wind Energy Development
on Reservation Lands
Indian tribal governments have the
authority to develop wind energy
projects, permit their development,
and establish relevant regulatory
guidance within the framework of
applicable laws.
The Service will provide technical
assistance upon the request
of Tribes that aim to establish
regulatory guidance for wind
energy development for lands under

Indian tribal governments may wish
to develop wind energy projects
on lands that are not held in trust
status. In such cases, the Tribes
should coordinate with agencies
other than the Service. At the
request of a Tribe, the Service may
facilitate discussions with other
regulatory organizations. The
Service may also lend its expertise
in these collaborative efforts to help
determine the extent to which tribal
resource management plans and
priorities can be incorporated into
established regulatory protocols.
Non-Tribal Wind Energy
Development – Consultation with
Indian Tribal Governments
When a non-Tribal wind energy
project is proposed that may affect a
Tribe’s resources (including cultural
resources), lands, rights, or ability
to govern or provide services to its
members, the Service should seek
to engage the affected Tribe(s) in
consultation and coordination as
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
early as possible in the process. In
siting a proposed project that has a
federal nexus, it is incumbent upon
the regulatory agency to notify
potentially affected Tribes of the
proposed activity. If the Service or
other federal agency determines
that a project may affect a Tribe(s),
they should notify the Tribe(s) of the
action at the earliest opportunity.
At the request of a Tribe, the
Service may facilitate and lend its
expertise in collaborating with other
organizations to help determine
the extent to which tribal resource
management plans and priorities
can be incorporated into established
regulatory protocols or project
implementation. This process ideally
should be agreed to by all involved
parties.
In the consultative process, Tribes
should be engaged as soon as
possible when a decision may affect a
Tribe(s). Decisions made that affect
Indian Tribal governments without
adequate federal effort to engage
Tribe(s) in consultation have been
overturned by the courts. See, e.g.,
Quechan Tribe v. U.S. Dep’t of the
Interior, No. 10cv2241 LAB (CAB),
2010 WL 5113197 (S.D. Cal. Dec. 15,
2010). When a tribal government
is consulted, it is neither required,
nor expected that all of the Tribe’s
issues can be resolved in its favor.
However, the Service must listen
and may not arbitrarily dismiss
concerns of the tribal government.
Rather, the Service must seriously
consider and respond to all tribal
concerns. Regional Native American
Liaisons are able to provide in-house
guidance as to government-togovernment consultation processes.
(See Service - State Coordination
and Cooperation, above).

meetings, and comment processes.
In the absence of formal public
process, there are many NGOs
that have substantial scientific
capabilities and may have resources
that could contribute productively to
the siting of wind energy projects.
Several NGOs have made significant
contributions to the understanding
of the importance of particular
geographic areas to wildlife in
the United States. This work has
benefited and continues to benefit
from extensive research efforts
and from associations with highly
qualified biologists. NGO expertise
can – as can scientific expertise in
the academic or private consulting
sectors – serve highly constructive
purposes. These can include:
• Providing information to
help identify environmentally
sensitive areas, during the
screening phases of site
selection (Tiers 1 and 2, as
described in this document)
• Providing feedback to
developers and agencies with
respect to specific sites and site
and impact assessment efforts
• Helping developers and agencies
design and implement mitigation
or offset strategies
• Participating in the defining,
assessing, funding, and
implementation of research
efforts in support of improved
predictors of risk, impact
assessments and effective
responses
• Articulating challenges,
concerns, and successes to
diverse audiences

Non-Governmental Organization
Actions

Non-Governmental Organization
Conservation Lands

If a specific project involves actions
at the local, state, or federal level
that provide opportunities for public
participation, non-governmental
organizations (NGOs) can provide
meaningful contributions to the
discussion of biological issues
associated with that project,
through the normal processes such
as scoping, testimony at public

Implementation of these Guidelines
by Service and other state agencies
will recognize that lands owned
and managed by non-government
conservation organizations
represent a significant investment
that generally supports the mission
of state and federal wildlife agencies.
Many of these lands represent an
investment of federal conservation

58 

funds, through partnerships
between agencies and NGOs. These
considerations merit extra care
in the avoidance of wind energy
development impacts to these lands.
In order to exercise this care, the
Service and allied agencies can
coordinate and consult with NGOs
that own lands or easements which
might reasonably be impacted by a
project under review.

U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Appendix A: Glossary
Accuracy – The agreement between a measurement and the true or correct value.
Adaptive management – An iterative decision process that promotes flexible decision-making that can be adjusted
in the face of uncertainties as outcomes from management actions and other events become better understood.
Comprehensively applying the tiered approach embodies the adaptive management process.
Anthropogenic – Resulting from the influence of human beings on nature.
Area of interest – For most projects, the area where wind turbines and meteorological (met) towers are proposed or
expected to be sited, and the area of potential impact.
Avian – Pertaining to or characteristic of birds.
Avoid – To not take an action or parts of an action to avert the potential effects of the action or parts thereof. First of
three components of “mitigation,” as defined in Service Mitigation Policy. (See mitigation.)
Before-after/control-impact (BACI) – A study design that involves comparisons of observational data, such as bird
counts, before and after an environmental disturbance in a disturbed and undisturbed site. This study design allows
a researcher to assess the effects of constructing and operating a wind turbine by comparing data from the “control”
sites (before and undisturbed) with the “treatment” sites (after and disturbed).
Best management practices (BMPs) – Methods that have been determined by the stakeholders to be the most
effective, practicable means of avoiding or minimizing significant adverse impacts to individual species, their habitats
or an ecosystem, based on the best available information.
Buffer zone – A zone surrounding a resource designed to protect the resource from adverse impact, and/or a
zone surrounding an existing or proposed wind energy project for the purposes of data collection and/or impact
estimation.
Community-scale – Wind energy projects greater than 1 MW, but generally less than 20 MW, in name-plate capacity,
that produce electricity for off-site use, often partially or totally owned by members of a local community or that have
other demonstrated local benefits in terms of retail power costs, economic development, or grid issues.
Comparable site – A site similar to the project site with respect to topography, vegetation, and the species under
consideration.
Compensatory mitigation – Replacement of project-induced losses to fish and wildlife resources. Substitution or
offsetting of fish and wildlife resource losses with resources considered to be of equivalent biological value.
- In-kind – Providing or managing substitute resources to replace the value of the resources lost, where such
substitute resources are physically and biologically the same or closely approximate to those lost.
- Out-of-kind – Providing or managing substitute resources to replace the value of the resources lost, where
such substitute resources are physically or biologically different from those lost. This may include conservation
or mitigation banking, research or other options.

Cost effective – Economical in terms of tangible benefits produced by money spent.
Covariate – Uncontrolled random variables that influence a response to a treatment or impact, but do not interact
with any of the treatments or impacts being tested.
Critical habitat – For listed species, consists of the specific areas designated by rule making pursuant to Section 4 of
the Endangered Species Act and displayed in 50 CFR § 17.11 and 17.12.
Cumulative impacts – See impact.
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Curtailment – The act of limiting the supply of electricity to the grid during conditions when it would normally be
supplied. This is usually accomplished by cutting-out the generator from the grid and/or feathering the turbine
blades.
Cut-in Speed – The wind speed at which the generator is connected to the grid and producing electricity. It is
important to note that turbine blades may rotate at full RPM in wind speeds below cut-in speed.
Displacement – The loss of habitat as result of an animal’s behavioral avoidance of otherwise suitable habitat.
Displacement may be short-term, during the construction phase of a project, temporary as a result of habituation, or
long-term, for the life of the project.
Distributed wind – Small and mid-sized turbines between 1 kilowatt and 1 megawatt that are installed and produce
electricity at the point of use to off-set all or a portion of on-site energy consumption.
Ecosystem – A system formed by the interaction of a community of organisms with their physical and chemical
environment. All of the biotic elements (i.e., species, populations, and communities) and abiotic elements (i.e., land,
air, water, energy) interacting in a given geographic area so that a flow of energy leads to a clearly defined trophic
structure, biotic diversity, and material cycles. Service Mitigation Policy adopted definition from E. P. Odum 1971
Fundamentals of Ecology.
Edge effect – The effect of the juxtaposition of contrasting environments on an ecosystem.
Endangered species – See listed species.
Extirpation – The species ceases to exist in a given location; the species still exists elsewhere.
Fatality – An individual instance of death.
Fatality rate – The ratio of the number of individual deaths to some parameter of interest such as megawatts of
energy produced, the number of turbines in a wind project, the number of individuals exposed, etc., within a specified
unit of time.
Feathering – Adjusting the angle of the rotor blade parallel to the wind, or turning the whole unit out of the wind, to
slow or stop blade rotation.
Federal action agency – A department, bureau, agency or instrumentality of the United States which plans,
constructs, operates or maintains a project, or which reviews, plans for or approves a permit, lease or license for
projects, or manages federal lands.
Federally listed species – See listed species.
Footprint – The geographic area occupied by the actual infrastructure of a project such as wind turbines, access
roads, substation, overhead and underground electrical lines, and buildings, and land cleared to construct the
project.
G1 (Global Conservation Status Ranking) Critically Imperiled – At very high risk of extinction due to extreme rarity
(often five or fewer populations), very steep declines, or other factors.
G2 (Global Conservation Status Ranking) Imperiled – At high risk of extinction or elimination due to very restricted
range, very few populations, steep declines, or other factors.
G3 (Global Conservation Status Ranking) Vulnerable – At moderate risk of extinction or elimination due to a restricted
range, relatively few populations, recent and widespread declines, or other factors.
Guy wire – Wires used to secure wind turbines or meteorological towers that are not self-supporting.
Habitat – The area which provides direct support for a given species, including adequate food, water, space, and cover
necessary for survival.
Habitat fragmentation – Habitat fragmentation separates blocks of habitat for some species into segments, such that
the individuals in the remaining habitat segments may suffer from effects such as decreased survival, reproduction,
distribution, or use of the area.
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Impact – An effect or effects on natural resources and on the components, structures, and functioning of affected
ecosystems.
- Cumulative – Changes in the environment caused by the aggregate of past, present and reasonably
foreseeable future actions on a given resource or ecosystem.
- Direct – Effects on individual species and their habitats caused by the action, and occur at the same time and
place.
- Indirect impact – Effects caused by the action that are later in time or farther removed in distance, but are
still reasonably foreseeable. Indirect impacts include displacement and changes in the demographics of bird
and bat populations.

Infill – Add an additional phase to the existing project, or build a new project adjacent to existing projects.
In-kind compensatory mitigation – See compensatory mitigation.
Intact habitat – An expanse of habitat for a species or landscape scale feature, unbroken with respect to its value for
the species or for society.
Intact landscape – Relatively undisturbed areas characterized by maintenance of most original ecological processes
and by communities with most of their original native species still present.
Lattice design – A wind turbine support structure design characterized by horizontal or diagonal lattice of bars
forming a tower rather than a single tubular support for the nacelle and rotor.
Lead agency – Agency that is responsible for federal or non-federal regulatory or environmental assessment actions.
Lek – A traditional site commonly used year after year by males of certain species of birds (e.g., greater and lesser
prairie-chickens, sage and sharp-tailed grouse, and buff-breasted sandpiper), within which the males display
communally to attract and compete for female mates, and where breeding occurs.
Listed species – Any species of fish, wildlife or plant that has been determined to be endangered or threatened under
section 4 of the Endangered Species Act (50 CFR §402.02), or similarly designated by state law or rule.
Local population – A subdivision of a population of animals or plants of a particular species that is in relative
proximity to a project.
Loss – As used in this document, a change in wildlife habitat due to human activities that is considered adverse and:
1) reduces the biological value of that habitat for species of concern; 2) reduces population numbers of species of
concern; 3) increases population numbers of invasive or exotic species; or 4) reduces the human use of those species
of concern.
Megawatt (MW) – A measurement of electricity-generating capacity equivalent to 1,000 kilowatts (kW), or 1,000,000

watts.

Migration – Regular movements of wildlife between their seasonal ranges necessary for completion of the species

lifecycle.

Migration corridor – Migration routes and/or corridors are the relatively predictable pathways that a migratory
species travel between seasonal ranges, usually breeding and wintering grounds.
Migration stopovers – Areas where congregations of wildlife assemble during migration. Such areas supply high
densities of food or shelter.
Minimize – To reduce to the smallest practicable amount or degree.
Mitigation – (Specific to these Guidelines) Avoiding or minimizing significant adverse impacts, and when appropriate,
compensating for unavoidable significant adverse impacts.

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Monitoring – 1) A process of project oversight such as checking to see if activities were conducted as agreed or
required; 2) making measurements of uncontrolled events at one or more points in space or time with space and time
being the only experimental variable or treatment; 3) making measurements and evaluations through time that are
done for a specific purpose, such as to check status and/or trends or the progress towards a management objective.
Mortality rate – Population death rate, typically expressed as the ratio of deaths per 100,000 individuals in the
population per year (or some other time period).
Operational changes – Deliberate changes to wind energy project operating protocols, such as the wind speed
at which turbines “cut in” or begin generating power, undertaken with the object of reducing collision fatalities.
Considered separately from standard mitigation measures due to the fact that operational changes are considered as
a last resort and will rarely be implemented if a project is properly sited.
Passerine – Describes birds that are members of the Order Passeriformes, typically called “songbirds.”
Plant communities of concern –Plant communities of concern are unique habitats that are critical for the persistence
of highly specialized or unique species and communities of organisms. Often restricted in distribution or represented
by a small number of examples, these communities are biological hotspots that significantly contribute to the
biological richness and productivity of the entire region. Plant communities of concern often support rare or
uncommon species assemblages, provide critical foraging, roosting, nesting, or hibernating habitat, or perform vital
ecosystem functions. These communities often play an integral role in the conservation of biological integrity and
diversity across the landscape. (Fournier et al. 2007) Also, any plant community with a Natural Heritage Database
ranking of S1, S2, S3, G1, G2, or G3.
Population – A demographically and genetically self-sustaining group of animals and/or plants of a particular species.
Practicable – Capable of being done or accomplished; feasible.
Prairie grouse – A group of gallinaceous birds, includes the greater prairie-chicken, the lesser prairie-chicken, and
the sharp-tailed grouse.
Project area – The area that includes the project site as well as contiguous land that shares relevant characteristics.
Project commencement – The point in time when a developer begins its preliminary evaluation of a broad geographic
area to assess the general ecological context of a potential site or sites for wind energy project(s). For example, this
may include the time at which an option is acquired to secure real estate interests, an application for federal land use
has been filed, or land has been purchased.
Project Site – The land that is included in the project where development occurs or is proposed to occur.
Project transmission lines – Electrical lines built and owned by a project developer.
Raptor – As defined by the American Ornithological Union, a group of predatory birds including hawks, eagles,
falcons, osprey, kites, owls, vultures and the California condor.
Relative abundance – The number of organisms of a particular kind in comparison to the total number of organisms
within a given area or community.
Risk – The likelihood that adverse effects may occur to individual animals or populations of species of concern, as a
result of development and operation of a wind energy project. For detailed discussion of risk and risk assessment as
used in this document see Chapter One - General Overview.
Rotor – The part of a wind turbine that interacts with wind to produce energy. Consists of the turbine’s blades and
the hub to which the blades attach.
Rotor-swept area – The area of the circle or volume of the sphere swept by the turbine blades.
Rotor-swept zone – The altitude within a wind energy project which is bounded by the upper and lower limits of the
rotor-swept area and the spatial extent of the project.

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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
S1 (Subnational Conservation Status Ranking) Critically Imperiled – Critically imperiled in the jurisdiction because of
extreme rarity or because of some factor(s) such as very steep declines making it especially vulnerable to extirpation
from the jurisdiction.
S2 (Subnational Conservation Status Ranking) Imperiled – Imperiled in the jurisdiction because of rarity due to very
restricted range, very few populations, steep declines, or other factors making it very vulnerable to extirpation from
jurisdiction.
S3 (Subnational Conservation Status Ranking) Vulnerable – Vulnerable in the jurisdiction due to a restricted range,
relatively few populations, recent and widespread declines, or other factors making it vulnerable to extirpation.
Sage grouse – A large gallinaceous bird living in the sage steppe areas of the intermountain west, includes the
greater sage grouse and Gunnison’s sage grouse.
Significant – For purposes of characterizing impacts to species of concern and their habitats, “significance” takes
into account the duration, scope, and intensity of an impact. Impacts that are very brief or highly transitory, do
not extend beyond the immediate small area where they occur, and are minor in their intensity are not likely to
be significant. Conversely, those that persist for a relatively long time, encompass a large area or extend well
beyond the immediate area where they occur, or have substantial consequences are almost certainly significant. A
determination of significance may include cumulative impacts of other actions. There is probably some unavoidable
overlap among these three characteristics, as well as some inherent ambiguity in these terms, requiring the exercise
of judgment and the development of a consistent approach over time.
Species of concern – For a particular wind energy project, any species which 1) is either a) listed as an endangered,
threatened or candidate species under the Endangered Species Act, subject to the Migratory Bird Treaty Act or
Bald and Golden Eagle Protection Act; b) is designated by law, regulation, or other formal process for protection and/
or management by the relevant agency or other authority; or c) has been shown to be significantly adversely affected
by wind energy development, and 2) is determined to be possibly affected by the project.
Species of habitat fragmentation concern—Species of concern for which a relevant federal, state, tribal, and/or local
agency has found that separation of their habitats into smaller blocks reduces connectivity such that the individuals
in the remaining habitat segments may suffer from effects such as decreased survival, reproduction, distribution, or
use of the area. Habitat fragmentation from a wind energy project may create significant barriers for such species.
String – A number of wind turbines oriented in close proximity to one another that are usually sited in a line, such as
along a ridgeline.
Strobe – Light consisting of pulses that are high in intensity and short in duration.
Threatened species – See listed species.
Tubular design – A type of wind turbine support structure for the nacelle and rotor that is cylindrical rather than
lattice.
Turbine height – The distance from the ground to the highest point reached by the tip of the blades of a wind turbine.
Utility-scale – Wind projects generally larger than 20 MW in nameplate generating capacity that sell electricity
directly to utilities or into power markets on a wholesale basis.
Voltage (low and medium) – Low voltages are generally below 600 volts, medium voltages are commonly on
distribution electrical lines, typically between 600 volts and 110 kV, and voltages above 110 kV are considered high
voltages.
Wildlife – Birds, fishes, mammals, and all other classes of wild animals and all types of aquatic and land vegetation
upon which wildlife is dependent.
Wildlife management plan – A document describing actions taken to identify resources that may be impacted by
proposed development; measures to mitigate for any significant adverse impacts; any post-construction monitoring;
and any other studies that may be carried out by the developer.
Wind turbine – A machine for converting the kinetic energy in wind into mechanical energy, which is then converted
to electricity..
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines

Appendix B: Literature Cited
Anderson, R., M. Morrison, K. Sinclair, and D. Strickland. 1999. Studying Wind Energy/Bird Interactions: A
Guidance Document. Metrics and Methods for Determining or Monitoring Potential Impacts on Birds at
Existing and Proposed Wind Energy Sites. National Wind Coordinating Committee/RESOLVE. Washington,
D.C., USA.
Arnett, E.B., and J.B. Haufler. 2003. A customer-based framework for funding priority research on bats and their
habitats. Wildlife Society Bulletin 31 (1): 98–103.
Arnett, E.B., technical editor. 2005. Relationships between Bats and Wind Turbines in Pennsylvania and West
Virginia: An Assessment of Bat Fatality Search Protocols, Patterns of Fatality, and Behavioral Interactions
with Wind Turbines. A final report submitted to the Bats and Wind Energy Cooperative. Bat Conservation
International. Austin, Texas, USA. http://www.batsandwind.org/pdf/ar2004.pdf
Arnett, E.B., J.P. Hayes, and M.M.P. Huso. 2006. An evaluation of the use of acoustic monitoring to predict bat
fatality at a proposed wind facility in south-central Pennsylvania. An annual report submitted to the Bats and
Wind Energy Cooperative. Bat Conservation International. Austin, Texas, USA.

http://batsandwind.org/pdf/ar2005.pdf.

Arnett, E.B., D.B. Inkley, D.H. Johnson, R.P. Larkin, S. Manes, A.M. Manville, R. Mason, M. Morrison, M.D.
Strickland, and R. Thresher. 2007. Impacts of Wind Energy Facilities on Wildlife and Wildlife Habitat. Issue
2007-2. The Wildlife Society, Bethesda, Maryland, USA.
Arnett, E.B., K. Brown, W.P. Erickson, J. Fiedler, B. Hamilton, T.H. Henry, G. D. Johnson, J. Kerns, R.R. Kolford,
C.P. Nicholson, T. O’Connell, M. Piorkowski, and R. Tankersley, Jr. 2008. Patterns of fatality of bats at wind
energy facilities in North America. Journal of Wildlife Management 72: 61–78.
Arnett, E.B., M. Schirmacher, M.M.P. Huso, and J.P. Hayes. 2009. Effectiveness of changing wind turbine cut-in
speed to reduce bat fatalities at wind facilities. An annual report submitted to the Bats and Wind Energy
Cooperative. Bat Conservation International. Austin, Texas, USA.

http://batsandwind.org/pdf/Curtailment_2008_Final_Report.pdf.

Arnett, E.B., M. Baker, M.M.P. Huso, and J. M. Szewczak. In review. Evaluating ultrasonic emissions to reduce bat
fatalities at wind energy facilities. An annual report submitted to the Bats and Wind Energy Cooperative. Bat
Conservation International. Austin, Texas, USA.
Avian Powerline Interaction Committee (APLIC). 2006. Suggested Practices for Avian Protection on Power Lines:
The State of the Art in 2006. Edison Electric Institute, APLIC, and the California Energy Commission.
Washington D.C. and Sacramento, CA. http://www.aplic.org/SuggestedPractices2006(LR-2watermark).pdf.
Baerwald, E.F., J. Edworthy, M. Holder, and R.M.R. Barclay. 2009. A Large-Scale Mitigation Experiment to Reduce
Bat Fatalities at Wind Energy Facilities. Journal of Wildlife Management 73(7): 1077-81.
Bailey, L.L., T.R. Simons, and K.H. Pollock. 2004. Spatial and Temporal Variation in Detection Probability of
Plethodon Salamanders Using the Robust Capture-Recapture Design. Journal of Wildlife Management 68(1):
14-24.
Becker, J.M., C.A. Duberstein, J.D. Tagestad, J.L. Downs. 2009. Sage-Grouse and Wind Energy: Biology, Habits, and
Potential Effects from Development. Prepared for the U.S. Department of Energy, Office of Energy Efficiency
and Renewable Energy, Wind & Hydropower Technologies Program, under Contract DE-AC05-76RL01830.
Breidt, F.J. and W.A. Fuller. 1999. Design of supplemented panel surveys with application to the natural resources
inventory. Journal of Agricultural, Biological, and Environmental Statistics 4(4): 391-403.
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U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines
Bright J., R. Langston, R. Bullman, R. Evans, S. Gardner, and J. Pearce-Higgins. 2008. Map of Bird Sensitivities to
Wind Farms in Scotland: A Tool to Aid Planning and Conservation. Biological Conservation 141(9): 2342-56.
California Energy Commission and California Department of Fish and Game. 2007. California Guidelines for
Reducing Impacts to Birds and Bats from Wind Energy Development. Commission Final Report. California
Energy Commission, Renewables Committee, and Energy Facilities Siting Division, and California Department
of Fish and Game, Resources Management and Policy Division. CEC-700-2007-008-CMF.
Chamberlain, D.E., M.R. Rehfisch, A.D. Fox, M. Desholm, and S.J. Anthony. 2006. The Effect of Avoidance Rates on
Bird Mortality Predictions Made by Wind Turbine Collision Risk Models. Ibis 148(S1): 198-202.
“Clean Water Act.” Water Pollution Prevention and Control. Title 33 U.S. Code, Sec. 1251 et. seq. 2006 ed., 301-482.
Print.
Connelly, J.W., H.W. Browers, and R.J. Gates. 1988. Seasonal Movements of Sage Grouse in Southeastern Idaho.
Journal of Wildlife Management 52(1): 116-22.
Connelly, J.W., M.A. Schroeder, A.R. Sands, and C.E. Braun. 2000. Guidelines to manage sage grouse population and
their habitats. Wildlife Society Bulletin 28(4):967-85.
Corn, P.S. and R.B. Bury. 1990. Sampling Methods for Terrestrial Amphibians and Reptiles, Gen. Tech. Rep. PNWGTR-256. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.
Cryan, P.M. 2008. Mating Behavior as a Possible Cause of Bat Fatalities at Wind Turbines. Journal of Wildlife
Management 72(3): 845-49.
Dettmers, R., D.A. Buehler, J.G. Bartlett, and N.A. Klaus. 1999. Influence of Point Count Length and Repeated
Visits on Habitat Model Performance. Journal of Wildlife Management 63(3): 815-23.
Drewitt, A.L. and R.H.W. Langston. 2006. Assessing the Impacts of Wind Farms on Birds. Ibis 148: 29-42.
Erickson, W.P., M.D. Strickland, G.D. Johnson, and J.W. Kern. 2000b. Examples of Statistical Methods to Assess Risk
of Impacts to Birds from Windplants. Proceedings of the National Avian-Wind Power Planning Meeting III.
National Wind Coordinating Committee, c/o RESOLVE, Inc., Washington, D.C.
Erickson, W.P., J. Jeffrey, K. Kronner, and K. Bay. 2004. Stateline Wind Project Wildlife Monitoring Final Report:
July 2001 - December 2003. Technical report for and peer-reviewed by FPL Energy, Stateline Technical
Advisory Committee, and the Oregon Energy Facility Siting Council, by Western EcoSystems Technology,
Inc. (WEST), Cheyenne, Wyoming, and Walla Walla, Washington, and Northwest Wildlife Consultants (NWC),
Pendleton, Oregon, USA. December 2004. http://www.west-inc.com.
Erickson, W., D. Strickland, J.A. Shaffer, and D.H. Johnson. 2007. Protocol for Investigating Displacement Effects
of Wind Facilities on Grassland Songbirds. National Wind Coordinating Collaborative, Washington, D. C. http://
www.nationalwind.org/workgroups/wildlife/SongbirdProtocolFinalJune07.pdf
Fiedler, J.K., T.H. Henry, C.P. Nicholson, and R.D. Tankersley. 2007. Results of Bat and Bird Mortality Monitoring
at the Expanded Buffalo Mountain Windfarm, 2005. Tennessee Valley Authority, Knoxville, Tennessee, USA.
https://www.tva.gov/environment/bmw_report/results.pdf
Fournier, D., J. Fraser, M. Coppoletta, M. Johnson, B. Brady, S. Dailey, B. Davidson, M. Vollmer, E. Carey, E.
Kelchin, C. Shade, A. Stanton, M. Morrison. 2007. Technical Supplement and Appendix for PATHWAY 2007
Evaluation Report: Vegetation Resource, Draft. Tahoe Regional Planning Agency.
Fuller, W.A. 1999. Environmental surveys over time. Journal of Agricultural, Biological, and Environmental Statistics
4(4): 331-45.
Gauthreaux, S.A., Jr., and C.G. Belser. 2003. Radar ornithology and biological conservation. Auk 120(2):266–77.
Giesen, K.M. and J.W. Connelly. 1993. Guidelines for management of Columbian sharp-tailed grouse habitats.
Wildlife Society Bulletin 21(3):325-33.

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Graeter, G.J., B.B. Rothermel, and J.W. Gibbons. 2008. Habitat Selection and Movement of Pond-Breeding
Amphibians in Experimentally Fragmented Pine Forests. Journal of Wildlife Management 72(2): 473-82.
Hagen, C.A., B.E. Jamison, K.M. Giesen, and T.Z. Riley. 2004. Guidelines for managing lesser prairie-chicken
populations and their habitats. Wildlife Society Bulletin 32(1):69-82.
Hagen, C.A., B.K. Sandercock, J.C. Pitman, R.J. Robel, and R.D. Applegate. 2009. Spacial variation in lesser prairiechicken demography: a sensitivity analysis of population dynamics and management alternatives. Journal of
Wildlife Management 73:1325-32.
Hagen, C.A., J.C. Pitman, T.M. Loughin, B.K. Sandercock, and R.J. Robel. 2011. Impacts of anthropogenic features
on lesser prairie-chicken habitat use. Studies in Avian Biology. 39: 63-75.
Holloran, M.J. 2005. Greater Sage-Grouse (Centrocercus urophasianus) Population Response to Natural Gas Field
Development in Western Wyoming. Ph.D. dissertation. University of Wyoming, Laramie, Wyoming, USA.
Holloran, M.J., B.J. Heath, A.G. Lyon, S.J. Slater, J.L. Kuipers, S.H. Anderson. 2005. Greater Sage-Grouse Nesting
Habitat Selection and Success in Wyoming. Journal of Wildlife Management 69(2): 638-49.
Horn, J.W., E.B. Arnett and T.H Kunz. 2008. Behavioral responses of bats to operating wind turbines. Journal of
Wildlife Management 72(1):123-32.
Hunt, G. 2002. Golden Eagles in a Perilous Landscape: Predicting the Effects of Mitigation for Wind Turbine
Bladestrike Mortality. California Energy Commission Report P500-02-043F. Sacramento, California, USA.
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Johnson, G.D., D.P. Young, Jr., W.P. Erickson, C.E. Derby, M.D. Strickland, and R.E. Good. 2000. Wildlife Monitoring
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Johnson, G.D., W.P. Erickson, and J. White. 2003. Avian and Bat Mortality During the First Year of Operation at
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Northwestern Wind Power, Goldendale, Washington, by Western EcoSystems Technology, Inc. (WEST),
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Kerns, J. and P. Kerlinger. 2004. A Study of Bird and Bat Collision Fatalities at the Mountaineer Wind Energy
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Methods for Mammals. Smithsonian Institution Press, Washington, D.C. USA. pp. 122-46.

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Kunz, T. H., E. B. Arnett, B. M. Cooper, W. P. Erickson, R. P. Larkin, T. Mabee, M. L. Morrison, M. D. Strickland, and
J. M. Szewczak. 2007. Assessing impacts of wind-energy development on nocturnally active birds and bats: a
guidance document. Journal of Wildlife Management 71: 2449-2486.
Kunz, T.H. and S. Parsons, eds. 2009. Ecological and Behavioral Methods for the Study of Bats. Second Edition.
Johns Hopkins University Press.
Leddy, K.L., K.F. Higgins, and D.E. Naugle. 1999. Effects of Wind Turbines on Upland Nesting Birds in
Conservation Reserve Program Grasslands. Wilson Bulletin 111(1): 100-4.
Mabee, T. J., B. A. Cooper, J. H. Plissner, and D. P. Young. 2006. Nocturnal bird migration over an Appalachian ridge
at a proposed wind power project. Wildlife Society Bulletin 34(3): 682–90.
Madders, M. and D.P. Whitfield. 2006. Upland Raptors and the Assessment of Wind Farm Impacts. Ibis 148: 43-56.
Manly, B.F., L. McDonald, D.L. Thomas, T.L. McDonald, and W.P. Erickson. 2002. Resource Selection by Animals:
Statistical Design and Analysis for Field Studies. 2nd Edition. Kluwer, Boston.
Manly, B.F.J. 2009. Statistics for Environmental Science and Management. 2nd edition. CRC Press, Boca Raton,
Florida, USA.
Manville, A. M. II. 2004. Prairie grouse leks and wind turbines: U.S. Fish and Wildlife Service justification for
a 5-mile buffer from leks; additional grassland songbird recommendations. Division of Migratory Bird
Management, Service, Arlington, VA, peer-reviewed briefing paper.
Master, L.L., B.A. Stein, L.S. Kutner and G.A. Hammerson. 2000. Vanishing Assets: Conservation Status of
U.S. Species. pp. 93-118 IN B.A. Stein, L.S. Kutner and J.S. Adams (eds.). Precious Heritage: the Status of
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McDonald, T.L. 2003. Review of environmental monitoring methods: survey designs. Environmental Monitoring and
Assessment 85(2): 277-92.
Morrison, M.L., W.M. Block, M.D. Strickland, B.A. Collier, and M.J. Peterson. 2008. Wildlife Study Design. Second
Edition. Springer, New York, New York, USA. 358 pp.
Murray, C. and D. Marmorek. 2003. Chapter 24: Adaptive Management and Ecological Restoration. In: P. Freiderici
(ed.), Ecological Restoration of Southwestern Ponderosa Pine Forests. Island Press, Washington, California,
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O’Farrell, M.J., B.W. Miller, and W.L. Gannon. 1999. Qualitative Identification of Free-Flying Bats Using the Anabat
Detector. Journal of Mammalogy 80(1): 11-23.
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and Solano Counties, and the California Energy Commission by Biosystems Analysis, Inc., Tiburon, California,
USA.

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Pearce-Higgins, J.W., L. Stephen, R.H.W. Langston, & J.A. Bright. (2008) Assessing the cumulative impacts of wind
farms on peatland birds: a case study of golden plover Pluvialis apricaria in Scotland. Mires and Peat, 4(01), 1–
13.
Pennsylvania Game Commission (PGC). 2007. Wind Energy Voluntary Cooperation Agreement. Pennsylvania Game
Commission, USA. http://www.pgc.state.pa.us/pgc/lib/pgc/programs/voluntary_agreement.pdf
Pierson, E.D., M.C. Wackenhut, J.S. Altenbach, P. Bradley, P. Call, D.L. Genter, C.E. Harris, B.L. Keller, B. Lengas,
L. Lewis, B. Luce, K.W. Navo, J.M. Perkins, S. Smith, and L. Welch. 1999. Species Conservation Assessment
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Pitman, J.C., C.A. Hagen, R.J. Robel, T.M. Loughlin, and R.D. Applegate. 2005. Location and Success of Lesser
Prairie-Chicken Nests in Relation to Vegetation and Human Disturbance. Journal of Wildlife Management
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Pruett, C.L., M.A. Patten and D.H. Wolfe. Avoidance Behavior by Prairie Grouse: Implications for Development of
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Rainey, W.E. 1995. Tools for Low-Disturbance Monitoring of Bat Activity. In: Inactive Mines as Bat Habitat:
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Ralph, C.J., J.R. Sauer, and S. Droege, eds. 1995. Monitoring Bird Populations by Point Counts. U.S. Department of
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Smallwood, K.S. and C.G. Thelander. 2005. Bird Mortality at the Altamont Pass Wind Resource Area: March 1998 September 2001. Final report to the National Renewable Energy Laboratory, Subcontract No. TAT-8-18209-01
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with high resolution radar, ceilometers, and census. The Auk 118(2):389-403.
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Technical Guide. Adaptive Management Working Group, U.S. Department of the Interior, Washington, DC.

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Appendix C: Sources of Information Pertaining to
Methods to Assess Impacts to Wildlife
The following is an initial list of references that provide further information on survey and monitoring methods.
Additional sources may be available.
Anderson, R., M. Morrison, K. Sinclair, D. Strickland. 1999. Studying wind energy and bird interactions: a guidance
document. National Wind Coordinating Collaborative (NWCC). Washington, D.C.
Bird D.M., and K.L. Bildstein, (eds). 2007. Raptor Research and Management Techniques. Hancock House
Publishers, Surrey, British Columbia.
Braun. C.E. (ed). 2005. Techniques for Wildlife Investigations and Management. The Wildlife Society. Bethesda, MD.
California Bat Working Group. 2006. Guidelines for assessing and minimizing impacts to bats at wind energy
development sites in California. http://www.wbwg.org/conservation/papers/CBWGwindenergyguidelines.pdf
California Energy Commission and California Department of Fish and Game. 2007. California Guidelines for
Reducing Impacts to Birds and Bats from Wind Energy Development Commission Final Report. http://www.
energy.ca.gov/windguidelines/index.html
Corn, P.S. and R.B. Bury. 1990. Sampling Methods for Terrestrial Amphibians and Reptiles, Gen. Tech. Rep. PNWGTR-256. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.
Environment Canada’s Canadian Wildlife Service. 2006. Wind turbines and birds, a guidance document for
environmental assessment. March version 6. EC/CWS, Gatineau, Quebec. 50 pp.
Environment Canada’s Canadian Wildlife Service. 2006. Recommended protocols for monitoring impacts of wind
turbines and birds. July 28 final document. EC/CWS, Gatineau, Quebec. 33 pp.
Heyer, W.R., M.A. Donnelley, R.W. McDiarmid, L.C. Hayek, and M.S. Foster (Eds.) 1994. Measuring and monitoring
biological diversity: standard methods for amphibians. Smithsonian Institution Press. Washington, D.C., USA.
Knutson, M. G., N. P. Danz, T. W. Sutherland, and B. R. Gray. 2008. Landbird Monitoring Protocol for the U.S. Fish
and Wildlife Service, Midwest and Northeast Regions, Version 1. Biological Monitoring Team Technical Report
BMT-2008-01. U.S. Fish and Wildlife Service, La Crosse, WI.
Kunz, T.H., E.B. Arnett, B.M. Cooper, W.P. Erickson, R.P. Larkin, T. Mabee, M.L. Morrison, M.D. Strickland, and
J.M. Szewczak. 2007. Assessing impacts of wind-energy development on nocturnally active birds and bats: a
guidance document. Journal Wildlife Management 71:2249-2486.
Kunz, T.H. and S. Parsons, eds. 2009. Ecological and Behavioral Methods for the Study of Bats. Second Edition.
Johns Hopkins University Press.
Oklahoma Lesser-Prairie Chicken Spatial Planning Tool, at http://wildlifedepartment.com/lepcdevelopmentplanning.
htm, Citation: Horton, R., L. Bell, C. M. O’Meilia, M. McLachlan, C. Hise, D. Wolfe, D. Elmore and J.D.
Strong. 2010. A Spatially-Based Planning Tool Designed to Reduce Negative Effects of Development on the
Lesser Prairie-Chicken (Tympanuchus pallidicinctus) in Oklahoma: A Multi-Entity Collaboration to Promote
Lesser Prairie-Chicken Voluntary Habitat Conservation and Prioritized Management Actions. Oklahoma
Department of Wildlife Conservation. Oklahoma City, Oklahoma. 79 pp. http://www.wildlifedepartment.com/
lepcdevelopmentplanning.htm
Ralph, C. J., G. R. Geupel, P. Pyle, T.E. Martin, E. Thomas, D.F. DeSante. 1993. Handbook of field methods for
monitoring landbirds. Gen. Tech. Rep. PSW-GTR-144-www. Albany, CA: Pacific Southwest Research Station,
Forest Service, U.S. Department of Agriculture; 41 p.

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Ralph C.J, J.R. Sauer, S. Droege (Tech. Eds). 1995. Monitoring Bird Populations by Point Counts. U.S. Forest
Service General Technical Report PSW-GTR-149, Pacific Southwest Research Station, Albany, California. iv 187
pp.
Strickland, M.D., E.B. Arnett, W.P. Erickson, D.H. Johnson, G.D. Johnson, M.L. Morrison, J.A. Shaffer, and W.
Warren-Hicks. 2011. Comprehensive Guide to Studying Wind Energy/Wildlife Interactions. Prepared for the
National Wind Coordinating Collaborative, Washington, D.C. USA.
Wilson, D. E., F.R. Cole, J.D. Nichols, R. Rudra and M.S. Foster (Eds). 1996. Measuring and monitoring biological
diversity: standard methods for mammals. Smithsonian Institution Press. Washington, D.C., USA.

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http://www.fws.gov
March 2012