a

GAO

United States Government Accountability Office

Report to Congressional Requesters

September 2005 WIND POWER

Impacts on Wildlife 

and Government 

Responsibilities for 

Regulating 

Development and 

Protecting Wildlife

GAO-05-906
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

www.gao.gov/cgi-bin/getrpt?GAO-05-906.

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Robin Nazzaro 

at (202) 512-3841 or nazzaror@gao.gov. 

Highlights of GAO-05-906, a report to 

congressional requesters 

September 2005

WIND POWER

Impacts on Wildlife and Government 

Responsibilities for Regulating 

Development and Protecting Wildlife 

The impact of wind power facilities on wildlife varies by region and by 

species. Specifically, studies show that wind power facilities in northern 

California and in Pennsylvania and West Virginia have killed large numbers 

of raptors and bats, respectively. Studies in other parts of the country show 

comparatively lower levels of mortality, although most facilities have killed 

at least some birds. However, many wind power facilities in the United 

States have not been studied, and, therefore, scientists cannot draw 

definitive conclusions about the threat that wind power poses to wildlife in 

general. Further, much is still unknown about migratory bird flyways and 

overall species population levels, making it difficult to determine the 

cumulative impact that the wind power industry has on wildlife species. 

Notably, only a few studies exist concerning ways in which to reduce 

wildlife fatalities at wind power facilities. 

Regulating wind power facilities is largely the responsibility of state and 

local governments. In the six states GAO reviewed, wind power facilities are 

subject to local- or state-level processes, such as zoning ordinances to 

permit the construction and operation of wind power facilities. As part of 

this process, some agencies require environmental assessments before 

construction. However, regulatory agency officials do not always have 

experience or expertise to address environmental and wildlife impacts from 

wind power. The federal government plays a minimal role in approving wind 

power facilities, only regulating facilities that are on federal lands or have 

some form of federal involvement, such as receiving federal funds. In these 

cases, the wind power project must comply with federal laws, such as the 

National Environmental Policy Act, as well as any relevant state and local 

laws. 

Federal and state laws afford generalized protections to wildlife from wind 

power as with any other activity. The U.S. Fish and Wildlife Service (FWS) is 

the primary agency tasked with implementing wildlife protections in the 

United States. Three federal laws—the Migratory Bird Treaty Act, the Bald 

and Golden Eagle Protection Act, and the Endangered Species Act—

generally forbid harm to various species of wildlife. Although significant 

wildlife mortality events have occurred at wind power facilities, the federal 

government has not prosecuted any cases against wind power companies 

under these wildlife laws, preferring instead to encourage companies to take 

mitigation steps to avoid future harm. All of the six states GAO reviewed 

had statutes that can be used to protect some wildlife from wind power 

impacts; however, similar to FWS, no states have taken any prosecutorial 

actions against wind power facilities where wildlife mortalities have 

occurred. 

Wind power has recently 

experienced dramatic growth in the 

United States, with further growth 

expected. However, several wind 

power-generating facilities have 

killed migratory birds and bats, 

prompting concern from wildlife 

biologists and others about the 

species affected, and the 

cumulative effects on species 

populations. 

GAO assessed (1) what available 

studies and experts have reported 

about the impacts of wind power 

facilities on wildlife in the United 

States and what can be done to 

mitigate or prevent such impacts, 

(2) the roles and responsibilities of 

government agencies in regulating 

wind power facilities, and (3) the 

roles and responsibilities of 

government agencies in protecting 

wildlife. GAO reviewed a sample of 

six states with wind power 

development for this report. 

What GAO Recommends

GAO recommends that FWS 

provide state and local regulatory 

agencies with information on the 

potential wildlife impacts from 

wind power and the resources 

available to help make decisions 

about where wind power 

development should be approved. 

The Department of the Interior 

agreed with GAO’s 

recommendation. 
Page i GAO-05-906 Wind Power

Contents

Letter 1

Results in Brief 2

Background 5

Studies Show Wind Power Facility Impacts on Wildlife Vary, 

Although Notable Gaps in the Literature Remain and Few Studies 

Address Mitigation 10

Regulating Wind Power Facilities on Nonfederal Land Is Largely the 

Responsibility of State and Local Governments 21

Federal and State Laws Protect Wildlife 33

Conclusions 43

Recommendations for Executive Action 44

Agency Comments and Our Evaluation 44

Appendixes

Appendix I: Objectives, Scope, and Methodology 46

Appendix II: Studies of Bird, Bat, and Raptor Fatality Rates, by Region 49

Appendix III: Comments from the Department of the Interior 51

GAO Comments 54

Appendix IV: GAO Contact and Staff Acknowledgments 55

Bibliography 56

Tables Table 1: Type of Regulatory Process and Responsible Agency in 

Select States 22

Table 2: Federal Wildlife Protection Laws 34

Table 3: Studies of Bird, Bat, and Raptor Fatality Rates, by 

Region 49

Figures Figure 1: Installed Wind Power-Generating Capacity in Megawatts, 

by State, as of January 24, 2005 7

Figure 2: Areas of the United States with High Wind Potential 8

Figure 3: Example of Older Generation Wind Turbines in Altamont 

Pass, Northern California 12

Figure 4: Example of a Newer Generation Wind Power Facility 13

Figure 5: Wind Power Facility in Sherman County, Oregon 27

Figure 6: Wind Power Facility in Somerset County, 

Pennsylvania 28
Contents

Page ii GAO-05-906 Wind Power

Figure 7: Wind Power Facility in Tucker County, West Virginia 30

Abbreviations

BLM Bureau of Land Management

DOE Department of Energy

FWS U.S. Fish and Wildlife Service

MW megawatts

This is a work of the U.S. government and is not subject to copyright protection in the 

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Page 1 GAO-05-906 Wind Power

United States Government Accountability Office

Washington, D.C. 20548

A

September 16, 2005 Letr

The Honorable Nick J. Rahall, II

Ranking Democratic Member, Committee on Resources

House of Representatives

The Honorable Alan B. Mollohan

Ranking Democratic Member, Subcommittee on Science, 

 the Departments of State, Justice, and Commerce 

 and Related Agencies

Committee on Appropriations

House of Representatives

The production of wind power, a renewable energy source, has recently 

experienced dramatic growth in the United States, although it still 

generates less than 1 percent of the electricity used in this country. Wind 

power-generating facilities were first built in California about 25 years ago. 

Now wind power facilities can be found in over 30 states, and the industry 

is expected to continue to grow rapidly. The vast majority of wind power 

facilities are located in just 10 western and midwestern states; most are on 

nonfederal land. Development has slowly made its way east and is 

currently being pursued along the ridge tops of the Appalachian Mountains 

in Maryland, Pennsylvania, Virginia, and West Virginia. Once thought to 

have practically no adverse environmental effects, it is now recognized that 

wind power facilities can have adverse impacts—particularly on wildlife, 

and most significantly on birds and bats.

Large numbers of birds and bats are believed to follow and cross through 

many parts of the United States, including along mountain ridges, during 

their seasonal migrations. Consequently, wind power projects located in 

these areas could potentially impact these species. At wind 

power-generating facilities in Appalachia and California, wind turbines 

have killed large numbers of migratory birds and bats. Wind power 

facilities may also have other impacts on wildlife through alterations of 

habitat. Habitat destruction and modification is a leading threat to the 

continued survival of wildlife species in the United States.

In this context, we assessed (1) what available studies and experts have 

reported about the impacts of wind power facilities on wildlife in the 

United States and what can be done to mitigate or prevent such impacts, 

(2) the roles and responsibilities of government agencies in regulating wind 
Page 2 GAO-05-906 Wind Power

power facilities, and (3) the roles and responsibilities of government 

agencies in protecting wildlife.

To address these objectives, we reviewed major scientific studies and 

reports on direct impacts from wind power on avian species and other 

wildlife (we did not assess indirect impacts, such as habitat impacts). We 

interviewed experts from the Department of the Interior’s U.S. Fish and 

Wildlife Service (FWS), state agencies, academia, industry, and 

conservation groups and obtained their views on these studies and reports. 

We also reviewed a nonprobability sample of six states with wind power 

development—California, Minnesota, New York, Oregon, Pennsylvania, 

and West Virginia.1

 We selected these states to reflect a range in installed 

wind generating capacity, regulatory processes, history of wind power 

development, and geographic distribution and to reflect our requesters’ 

interests. We identified and reviewed relevant federal, state, and local laws 

and regulations. In addition, we interviewed federal, state, and local 

officials who were responsible for implementing related programs. More 

information about the objectives, scope, and methodology of our 

evaluation is presented in appendix I. We conducted our work between 

December 2004 and July 2005 in accordance with generally accepted 

government auditing standards, including an assessment of data reliability 

and internal controls.

Results in Brief Recent studies and interviews with experts indicate that the impacts of 

wind power facilities on birds and other wildlife vary by region and by 

species. Wildlife mortalities in two locations in particular have elicited 

concerns from scientists, regulators, and the public. Specifically, a recent 

study shows that over 1,000 raptors are killed by wind power facilities in 

northern California each year. Many experts attribute this large number of 

fatalities to unique aspects of wind power development in northern 

California, such as the unusually large number of turbines (over 5,000), the 

type of turbines in the region, and the presence of abundant raptor prey in 

the area. On the other side of the country, a recent study estimated that 

over 2,000 bats were killed during a 1-year period at a wind power facility in 

the mountains of eastern West Virginia. Studies from these two locations 

stand in contrast to studies from other wind power facilities. These studies 

1

Results from nonprobability samples cannot be used to make inferences about a population 

because in a nonprobability sample, some elements of the population being studied have no 

chance or an unknown chance of being selected as part of the sample.
Page 3 GAO-05-906 Wind Power

show relatively lower bird and bat mortality. However, bat estimates are 

less precise because most of the studies were designed to estimate only 

bird mortality. These studies have not elicited the same degree of concern 

from biologists as the studies from West Virginia and California. However, 

significant gaps in the literature make it difficult for scientists to draw 

conclusions about wind power’s impact on wildlife in general. For example, 

experts told us that there is a shortage of information on migratory bird 

routes and bat behavior as well as the ways in which topography, weather, 

and turbine type affect mortality. In addition, studies conducted at one 

location can rarely be used to extrapolate potential impacts or mitigation 

effectiveness at other locations because of differences in site-specific 

conditions, such as topography, the types and densities of species present, 

and the type of wind turbines installed. Finally, while some authors have 

recommended mitigation strategies for reducing bird and bat kills, there 

are relatively few comprehensive studies testing the effectiveness of these 

strategies.

Regulating wind power facilities on nonfederal land is largely the 

responsibility of state and local governments. In the six states we reviewed, 

the permitting of wind power development consisted of local-level 

processes, state-level processes, or a combination of the two. In California, 

New York, and Pennsylvania, local governments regulate the development 

of wind power. Local governments in these states generally require wind 

developers to adhere to local zoning ordinances and obtain special use 

permits before construction. In addition, California and New York have 

state environmental laws that require various studies and analyses to be 

conducted before a permit can be issued. West Virginia uses a state-level 

process, whereby its Public Service Commission is responsible for, among 

other things, regulating the activities of all public utilities operating in the 

state, including wind power. The commission has the authority to include 

certain conditions in wind power certificates, such as requiring wildlife 

studies before and after construction. In Minnesota and Oregon, local and 

state agencies regulate wind power development. In these two states, local 

agencies, such as county planning commissions or zoning boards, permit 

the development of wind power unless a project exceeds a certain level of 

electric-generating capacity; larger facilities are regulated by a state 

agency. While some state and local regulatory agencies require 

environmental assessments before construction, some state and local 

regulatory agency officials told us that they have little experience or 

expertise in addressing environmental and wildlife impacts from wind 

power. For example, officials in one state told us that they did not have the 

expertise to evaluate wildlife impacts and review studies prior to 
Page 4 GAO-05-906 Wind Power

construction. The federal government generally only has a regulatory role 

in wind power development when development occurs on federal land or 

involves some form of federal participation, such as providing funding for 

projects. In these cases, the development and operation of a wind power 

facility must comply with any state and local laws as well as federal laws, 

such as the National Environmental Policy Act and the Endangered Species 

Act—which often require preconstruction studies or analyses and possibly 

modifications to proposed projects to avoid adverse environmental effects.

As with any activity, federal and state laws afford protections to wildlife 

from wind power facilities. Three laws—the Migratory Bird Treaty Act, the 

Bald and Golden Eagle Protection Act, and the Endangered Species 

Act—are the federal laws most relevant to protecting wildlife from wind 

power facilities, and these laws generally forbid harm to various species of 

wildlife. FWS is the federal agency that has primary responsibility for 

implementing and enforcing these three laws. Although none of the three 

laws expressly require wind power developers and operators to take 

specific steps to ensure that wildlife will not be harmed during either the 

construction or operation of their facilities, wind power developers or 

operators are liable for any harm to protected species that may occur. In 

some cases, developers voluntarily consult with FWS—or a state natural 

resources agency—before they construct a project or they do so as a 

requirement of a state or local wind power regulatory agency, to identify 

potential impacts to wildlife. In other cases, federal involvement may 

consist of FWS law enforcement officials investigating instances of wildlife 

fatalities at a wind power facility. While significant mortality events have 

occurred at some wind power facilities—and, in some cases, are 

recurring—the federal government has not prosecuted any cases against 

wind power companies for violations of federal wildlife laws. In some 

cases, FWS has not taken action because the species killed are not 

federally protected, such as the bat species killed in West Virginia. In cases 

where violations of federal law have occurred, FWS law enforcement 

officials told us that before FWS pursues civil or criminal penalties, the 

agency prefers to work with companies to encourage them to take 

mitigation steps to avoid future harm. According to FWS officials, they 

have been reasonably successful in resolving impacts to wildlife by 

following this approach with the electric power industry. FWS has also 

referred cases against wind power developers to either the Interior’s Office 

of the Solicitor San Francisco field office or the Department of Justice for 

killing raptors, but Justice was unable to comment on the specifics of its 

ongoing investigation. FWS has been working with the wind industry to 

help identify solutions and ensure that wildlife mortality at wind power 
Page 5 GAO-05-906 Wind Power

facilities is minimized. For example, FWS has participated in 

industry-sponsored workshops and conferences, issued voluntary 

guidelines for industry to use in developing new projects, and served as a 

member in a wildlife working group with industry. Regarding state wildlife 

protections, all of the six states we reviewed have statutes that can be used 

to protect some wildlife from wind power impacts. However, similar to 

FWS, no states have taken any prosecutorial actions against wind power 

facilities where wildlife mortalities have occurred. 

To encourage potential wildlife impacts to be considered when wind power 

facilities are permitted, we are making a recommendation to FWS to reach 

out to state and local regulatory agencies with information on the potential 

wildlife impacts due to wind power and on the resources available to help 

make decisions about the siting of wind power facilities. 

We received written comments on a draft of this report. The Department of 

the Interior stated that they generally agree with our findings and our 

recommendation in the report. Written comments from the department are 

included in appendix III.

Background The energy used to generate our nation’s electricity comes from many 

different sources. Currently, most electricity in the United States is 

generated with fossil fuel and nuclear technologies—coal (52 percent), 

nuclear (20 percent), natural gas (16 percent), and oil (3 percent). Fossil 

fuels are considered nonrenewable because they are finite and will 

eventually dwindle or become too expensive or environmentally damaging 

to retrieve. Wind, however, is one of several sources of energy known as 

renewable energy. Other forms of renewable energy sources include 

sunlight (photovoltaics), heat from the sun (solar thermal), naturally 

occurring underground steam and heat (geothermal), plant and animal 

waste (biomass), and water (hydropower).

To reduce our dependence on nonrenewable energy sources, the United 

States has promoted the development of renewable resources, such as 

wind. A key federal program supporting the development of such sources is 

the federal production tax credit established by the Energy Policy Act of 

1992.2 This law provides a tax credit for electricity generated by renewable 

2

26 U.S.C. § 45. Section 1301 of the Energy Policy Act of 2005, Pub. L. No. 109-58, extended 

the tax credit through January 1, 2008.
Page 6 GAO-05-906 Wind Power

energy sources, such as wind turbines. The Economic Recovery Tax Act of 

1981 provides an additional incentive for wind power growth.3

 In some 

cases, this law allows a 5-year depreciation schedule for renewable energy 

systems. In conjunction with the tax credit, this accelerated depreciation 

allows an even greater tax break for renewable energy projects, such as 

wind projects, that have high initial capital costs.4

Some states also provide incentives for wind power development. One of 

the strongest drivers is a renewable portfolio standard. Generally, a 

renewable portfolio standard requires utilities operating in a state to 

acquire a minimum amount of their electricity supply from renewable 

energy sources. As of June 2005, 18 states had some form of renewable 

power requirements capable of being met by wind power. Other common 

types of incentives for renewable energy development provided by several 

state and local governments are income tax incentives and property and 

sales tax exemptions. Many states provide more than one type of incentive. 

In addition, 25 states have statewide wind working groups that are funded 

(at least partially) through grants from the Department of Energy (DOE). 

The purpose of these working groups is to promote more widespread 

development of wind power.

These federal and state programs have helped spur significant wind power 

development in the last 5 years. At the end of 2004, the total installed 

capacity from wind power in the United States was 6,740 megawatts (MW), 

or enough capacity to meet the electricity demand of between 1.5 and 2.0 

million average American households (see fig. 1). 

3

26 U.S.C. § 168(e)(3)(B)(vi).

4

See GAO, Renewable Energy: Wind Power’s Contribution to Electric Power Generation 

and Impact on Farms and Rural Communities, GAO-04-756 (Washington, D.C.: Sept. 3, 

2004) for prior work related to this issue.
Page 7 GAO-05-906 Wind Power

Figure 1: Installed Wind Power-Generating Capacity in Megawatts, by State, as of January 24, 2005

Between January 2000 and December 2004, installed electric-generating 

capacity more than doubled, adding over 4,200 MW of capacity. Although 

wind power generates less than 1 percent of the nation’s electricity, with an 

average annual growth rate of over 24 percent, it is the fastest growing 

source of electricity generation on a percentage basis. Because wind 

energy is a function of wind speed, the best locations for turbines are areas 

AR

NH

ID

UT

ME

MT

2

NE

14

AL

TN

29

ND

66

OK

176

SC

WI

53

MN

615

CO

229

MS

IA

632

VA

MO

IN

LA

SD

44

KS

114

GA

TX

1,293

OH

7

NV

NM

267

MD

DE

NJ

MI

2

NC

FL

IL

51

AZ

DC

PA

129

VT 6

WA

240

OR

263

WY

285

KY

WV

66

AK

1

HI

9

NY

48 MA 1

RI

CT

CA

2,096

Generating capacity (in megawatts)

Source: American Wind Energy Association.

None to <1.0

1.0 to < 100

100 to < 400 

400 to < 1,000

1,000 and above
Page 8 GAO-05-906 Wind Power

that have frequent strong winds to turn the blades of the power-generating 

turbines. See figure 2 for areas of the United States with high wind 

potential. 

Figure 2: Areas of the United States with High Wind Potential

Moderate

Good

Excellent

Resource potential

Source: Department of Energy, National Renewable Energy Laboratory.
Page 9 GAO-05-906 Wind Power

According to DOE, 36 of the 48 continental states have wind resources that 

would support utility-scale wind power projects (i.e., projects that generate 

at least 1 MW of electric power from 1 or more turbines annually for sale to 

a local utility). A DOE goal for wind power is to generate 5 percent of the 

electricity generated in the United States by 2020; the American Wind 

Energy Association has a similar goal.5

 To reach this goal, the association 

estimates that about 100,000 MW of installed capacity will be 

needed—approximately 15 times the current installed capacity. On the 

basis of the average MW size of wind turbines commonly being installed 

today (1.5 MW), more than 62,000 additional turbines will need to be added 

to the existing 16,000 turbines already constructed in the United States to 

meet such a goal. 

Most of the wind power development in the United States has occurred in 

10 western and midwestern states—California, Colorado, Iowa, Minnesota, 

New Mexico, Oklahoma, Oregon, Texas, Washington, and Wyoming. In fact, 

these 10 states have over 90 percent of the total installed wind power 

capacity nationwide. Only recently have developers begun to build wind 

energy facilities in the eastern United States. As shown in figure 2, wind 

power potential in this geographic area is best along mountain ridges, 

primarily the Appalachian Mountains, and along the coast of the 

northeastern United States. 

Wind power is considered a “green” technology because, unlike fossil fuel 

power plants, it does not produce harmful emissions, such as carbon 

dioxide, nitrogen oxides, sulfur dioxide, mercury, and particulate matter, 

which can pose human health and environmental risks such as acid rain. 

However, it is now recognized that wind power facilities can adversely 

affect the environment in other ways, specifically in impacting wildlife 

such as birds and bats. Wind power facilities located in migratory pathways 

or important habitats may harm the wildlife living or passing through the 

area by killing or injuring them or by disrupting feeding or breeding 

behaviors. But wind power is not alone in its impacts on wildlife. Millions, 

or perhaps billions, of wildlife are killed every year in the United States 

through a myriad of human activities. While sources of bat mortality are 

not as well known, FWS estimates that some of the leading sources of bird 

mortality, per year, are collisions with building windows—97 million to 976 

5

The American Wind Energy Association is a national trade association that represents wind 

power plant developers, wind turbine manufacturers, utilities, consultants, insurers, 

financiers, researchers, and others involved in the wind industry.
Page 10 GAO-05-906 Wind Power

million bird deaths, collisions with communication towers—4 million to 50 

million bird deaths, poisoning from pesticides—at least 72 million birds, 

and attacks by domestic and feral cats—hundreds of millions of bird 

deaths. Human activities also result in the destruction or modification of 

wildlife habitat; habitat loss and fragmentation are leading threats to the 

continued survival of many species. 

Studies Show Wind 

Power Facility Impacts 

on Wildlife Vary, 

Although Notable Gaps 

in the Literature 

Remain and Few 

Studies Address 

Mitigation 

Recent studies and interviews with experts reveal that the impacts of wind 

power facilities on birds and other wildlife vary by region and by species. 

Specifically, studies showing raptor mortality in California and bat 

mortality in Appalachia have elicited concerns from scientists, 

environmental groups, and regulators because of the large number of kills 

in these areas and the potential cumulative impact on some species. Thus 

far, documented bird and bat mortality from wind power in other parts of 

the country has not occurred in numbers high enough to raise concerns. 

However, gaps in the literature make it difficult to develop definitive 

conclusions about the impacts of wind power on birds and other wildlife. 

Notably, only a few studies have been conducted on strategies to address 

the potential risks wind power facilities pose to wildlife.

Wildlife Mortality Varies by 

Region and by Species

Our review of the literature and discussions with experts revealed that, 

thus far, concerns over direct impacts to wildlife from wind power facilities 

have been concentrated in two geographic areas—northern California and 

Appalachia.6

 (For a discussion on how we selected these studies, see app. 

I.) While bird and bat kills have been documented in many locations, 

biologists are primarily concerned about mortality in these two regions 

because of the numbers of wildlife killed and the species affected.

Studies Have Found Large 

Numbers of Raptors Killed by 

Wind Turbines in California

Wind power facilities in northern California, specifically in the Altamont 

Pass Wind Resource Area about 50 miles east of San Francisco, have been 

responsible for the deaths of numerous raptors, or birds of prey, such as 

hawks and golden eagles, and, as a result, these deaths have elicited 

concern from wildlife protection groups, biologists, and regulators. Studies 

conducted in the last two decades have documented large numbers of 

raptor deaths in this area. One study in our review found estimates as high 

6

Many of these studies were conducted by consultants for wind power companies and were 

not scientifically peer-reviewed. In addition, protocols used in these studies may vary. 
Page 11 GAO-05-906 Wind Power

as over 1,000 raptor deaths per year. Such large numbers of raptor kills due 

to wind power are not seen elsewhere in the United States. A 2001 

summary that examined raptor mortality rates from studies in 10 states 

estimated that over 90 percent of the raptors killed annually in the United 

States by wind power turbines occurred in California.7

Several unique features of the wind resource area at Altamont Pass 

contribute to the high number of raptor deaths. First, California was the 

first area to develop wind power in significant numbers and thus has some 

of the oldest turbines still in operation in the United States. Older turbines 

produce less power per turbine, so it took many turbines to produce a 

certain level of energy; today, newer facilities producing the same amount 

of energy would have much fewer turbines. For example, Altamont Pass 

has over 5,000 wind turbines—many of which are older models—whereas, 

newer facilities generally have significantly fewer turbines (see figs. 3 and 

4). Some experts told us that the sheer number of turbines in Altamont 

Pass has been a major reason for the high number of fatalities in the area. 

7

Erickson, Wallace P., Gregory D. Johnson, M. Dale Strickland, David P. Young Jr., Karyn J. 

Sernka, and Rhett E. Good. Avian Collisions with Wind Turbines: A Summary of Existing 

Studies and Comparisons to Other Sources of Avian Collision Mortality in the United 

States. A National Wind Coordinating Committee Resource Document, August 2001. 

Because summaries of studies generally do not present detailed information about the 

methodologies of the studies they include, these results should be considered with caution.
Page 12 GAO-05-906 Wind Power

Figure 3: Example of Older Generation Wind Turbines in Altamont Pass, Northern 

California

Source: California Energy Commission.
Page 13 GAO-05-906 Wind Power

Figure 4: Example of a Newer Generation Wind Power Facility 

Secondly, some scientists believe that the design of older generation 

turbines, like those found in Altamont Pass, are more fatal to raptors. 

Specifically, early turbines were mounted on towers 60 feet to 80 feet in 

height, while today’s turbines are mounted on towers 200 feet to 260 feet in 

height. Experts told us that the older turbines at Altamont Pass have blades 

that reach lower to the ground, and thus can be more hazardous to raptors 

as they swoop down to catch prey. Experts also reasoned that the relative 

absence of raptor kills at newer facilities with generally taller turbines 

supports the notion that these turbines are less lethal to raptors. Third, the 

location of the wind turbine facilities at Altamont Pass may have 

contributed to the high number of raptor deaths. Studies show that there 

are a high number of raptors that pass through the area, as well as an 

abundance of raptor prey at the base of the turbines. In addition, the 

location of wind turbines on ridge tops and canyons may increase the 

likelihood that raptors will collide with turbines. Some experts note that 

one reason why other parts of the country may not be experiencing high 

levels of raptor mortality is partly because wind developers have used 

information from Altamont Pass to site new turbines in hopes of avoiding 

similar situations. 

Source: Department of Energy, National Renewable Energy Laboratory.
Page 14 GAO-05-906 Wind Power

Studies Have Found Large 

Numbers of Bats Killed by Wind 

Turbines in Appalachia

Recent studies conducted in the eastern United States in the Appalachian 

Mountains have found large numbers of bats killed by wind power turbines. 

A 2004 study conducted in West Virginia estimated that slightly over 2,000 

bats were killed during a 7-month study at a location with 44 turbines. More 

recently, a 2005 report that examined wind resource areas both in West 

Virginia and Pennsylvania estimated that about 2,000 bats were killed 

during a much shorter 6-week study period at 64 turbines. Lastly, a study 

conducted of a small 3-turbine wind facility in Tennessee estimated that bat 

mortality was about 21 bats per turbine, per year, raising concerns about 

the potential impact on bats if more turbines are built in this area. 

Various species of bats have been killed at these wind power facilities and 

experts are concerned about impacts to bat populations if large numbers of 

deaths continue. For example, one expert noted that “it is alarming to see 

the number of bats currently being killed coupled with the proposed 

number of wind power developments” in these areas. He explained that 

bats live longer and have lower reproductive rates than birds, and, 

therefore, bat populations may be more vulnerable to impacts. In addition, 

there are proposals for hundreds of new wind turbines along the 

Appalachian Mountains. A recent report from Bat Conservation 

International estimated that if all ridge-top turbines are approved and the 

mortality rates continue at their current rate, these turbines might kill tens 

of thousands of bats in a single season. Although none of the bats killed by 

wind power to date have been listed as endangered species, FWS— 

recognizing the seriousness of the problem—has initiated a study with the 

U.S. Geological Survey to study bat migration and to develop decision tools 

to provide assistance in identifying locations for wind turbines and 

communication towers. 

Studies Show That Bird and Bat 

Mortality from Wind Power in 

Other Parts of the Country Is 

Comparatively Lower Than in 

California and Appalachia

Results from studies on bird and bat mortality from wind power conducted 

in areas other than northern California and Appalachia have not caused the 

same degree of concern as in these two locations. Our review of studies 

conducted in areas other than the Appalachian Mountains showed bat 

fatality rates ranging from 0 to 4.3 bats per turbine, per year—compared 

with rates as high as 38 bats per turbine, per a 6-week study period, in the 

Appalachian Mountains (see app. II). Raptor fatalities outside Altamont 

Pass ranged from 0 to 0.07 raptors per turbine, per year, whereas, rates in 

Altamont Pass ranged from 0.05 to 0.24. Our review of studies found that 

overall bird fatalities from wind power ranged from 0 to 7.28 birds per 

turbine, per year. In addition, a 2004 National Wind Coordinating 

Committee fact sheet shows that an average of 2.3 birds per turbine, per
Page 15 GAO-05-906 Wind Power

year are killed at facilities outside of California.8 However, it is important to 

also look at the number of turbines and the vulnerability of the species 

affected when interpreting these rates. For example, the high rate of 7.28 

overall bird fatalities per turbine was found at a facility of only 3 wind 

turbines. Therefore, if no additional turbines are built in this area, the 

overall impact to the bird populations may be minimal; whereas, a lower 

fatality rate may cause impacts if there are many turbines in that particular 

area. In addition, comparing study findings can be difficult because 

researchers may use differing metrics and many areas of the country 

remain unstudied with regard to avian and bat impacts from wind power. 

While interpreting these statistics can be complicated, the experts we 

spoke with agreed that outside of California and Appalachia at the current 

level of wind power development, the research to date has not shown bird 

or bat kills in alarming numbers.

While the studies we reviewed showed relatively low levels of mortality in 

many locations, there are also indirect impacts to wildlife from wind power 

facilities. For example, construction of wind power facilities may fragment 

habitat and disrupt feeding or breeding behaviors. According to FWS, the 

loss of habitat quantity and quality is the primary cause of declines in most 

assessed bird populations and many other wildlife species. However, this 

review focuses on the direct impacts of avian and bat mortality. 

Several Gaps Exist in 

Research on Wind Power 

Facility Impacts on Wildlife 

While experts told us that the impact of wind power facilities on wildlife is 

more studied than other comparable infrastructure, such as 

communication towers, important gaps in the research remain. First, 

relatively few postconstruction monitoring studies have been conducted 

and made publicly available. It appears that many wind power facilities and 

geographic areas in the United States have not been studied at all. For 

example, a bird advocacy group expressed concern at a recent National 

Wind Coordinating Committee meeting that most of the wind projects that 

have been monitored for bird impacts are in the west. The American Wind 

Energy Association reports that there are hundreds of wind power facilities 

currently operating elsewhere in the country. However, we were able to 

8

National Wind Coordinating Committee, Wind Turbine Interactions with Birds and Bats: 

A Summary of Research Results and Remaining Questions. Fact sheet: Second Edition. 

November 2004. Because summaries of studies generally do not present detailed 

information about the methodologies of the studies that they include, these results should 

be considered with caution.
Page 16 GAO-05-906 Wind Power

locate only 19 postconstruction studies that were conducted to assess 

direct impacts to birds or bats in 11 states.9

 Texas, for example, is second 

only to California in installed wind power capacity, but we were unable to 

find a single, publicly available study investigating bird or bat mortality in 

that state. 

Lack of comprehensive data on bird and bat fatalities from wind turbines 

makes it difficult to make national assessments of the impact of wind 

turbines on wildlife. A 2001 analysis of studies estimated that wind turbines 

in the United States cause roughly 33,000 avian deaths per year.10 However, 

the authors noted that making projections of the potential magnitude of 

wind power-related avian fatalities is problematic, in part, because of the 

lack of long-term data. The authors further noted that the data collected at 

older sites may not be representative of newer facilities with more modern 

turbine technology. In addition, FWS considers this estimate to be a 

“minimum” to “conservative” estimate due to problems of data collection 

and uneven regional representation. In addition to limiting assessments of 

national impacts, a lack of data on actual mortality impacts siting decisions 

for new facilities. Specifically, the conclusions of postconstruction studies 

are often used when making preconstruction predictions about the degree 

of harm to wildlife that is likely expected from proposed facilities. If there 

are no local postconstruction studies available, predictions of future 

mortality at a proposed site must be based on information from studies 

conducted in areas that may have different wildlife species, topography, 

weather conditions, climate, soil types, and vegetative cover.

A second important research gap is in understanding what factors increase 

the chances that turbines will be hazardous to wildlife. For example, it can 

be difficult to discern, among other things, how the number, location, and 

type of turbine; the number and type of species in an area; species 

behavior; topography; and weather affect mortality and why. Drawing 

conclusions about the degree of risk posed by certain factors—such as 

terrain, weather, or type of turbine—is difficult because sites differ in their 

combination of factors. For example, according to experts, data are 

inadequate about what turbine types are most hazardous and to what 

species. This is partly because most wind power facilities use only one 

9

See appendix I for the criteria we used for including studies in our review.

10Erickson, Wallace P., Gregory D. Johnson, M. Dale Strickland, David P. Young Jr., Karyn J. 

Sernka, and Rhett E. Avian Collisions with Wind Turbines.
Page 17 GAO-05-906 Wind Power

turbine type. Therefore, even if one facility proved more hazardous than 

another, it would be difficult to attribute the difference to turbine type 

alone because other variables, such as topography or migratory patterns, 

are also likely to vary among the sites. Additionally, comparisons between 

studies are difficult because researchers may use different study 

methodologies. Therefore, even if two sites had similar bird populations, 

topography, and weather characteristics but different turbines, it would be 

difficult to isolate the effect of the turbine if the scientists collecting the 

information used differing methodologies. 

Altamont Pass, however, has the potential to allow researchers to 

determine which turbines are more hazardous because it contains many 

different types of turbines in one place. However, even this analysis has 

been complicated by confounding variables. For example, according to 

experts, at one time it was commonly thought that turbines with lattice 

towers killed more birds than turbines with tubular towers in Altamont 

Pass; however, some studies have reached the opposite conclusion. One 

study noted that although the authors found higher mortality associated 

with lattice towers, this relationship might be explained by factors such as 

the fact that lattice towers were found to be in operation more frequently 

than were other towers, including tubular towers, rather than the 

difference in the design of the towers. Complicating matters still, some 

factors may be more hazardous for some species than others. One study 

found that red-tailed hawk fatalities occurred more frequently than 

expected at turbines located on ridgelines than on hillsides. The authors 

found the reverse to be true for golden eagles, demonstrating the difficulty 

of understanding interactions between turbines and bird mortality from 

bird mortality estimates alone.

A third research gap is the lack of complete and definitive information on 

the interaction of bats with wind turbines. As previously noted, bats have 

collided with wind turbines in significant numbers in some parts of the 

United States, but scientists do not have a complete understanding 

regarding why these collisions occur. Bats are known to have the ability to 

echolocate to avoid collision with objects, and they have been able to avoid 

colliding with comparable structures such as meteorological towers.11

Therefore, their collision with wind turbines remains a mystery. The few 

studies that have been conducted show that most of the kills have taken 

11Meteorological towers are used to assess weather conditions, including wind speed and 

direction.
Page 18 GAO-05-906 Wind Power

place during the migratory season (July through September), and this 

suggests that migrating bats are involved in most of the fatalities. In 

addition, one study showed that lower wind speeds were associated with 

higher fatality rates. However, experts admit that much remains unknown 

about why bats are attracted to and killed by turbines and about what 

conditions increase the chances that bats will be killed. One expert noted 

that there is still very little known about bat migration in general and about 

the way in which bat interactions with turbines are affected by weather 

patterns. This expert further noted that there still has not been a full season 

of monitoring bat mortality from which patterns can be identified. 

Although scientists still do not know why bats are being killed in large 

numbers by wind power turbines in some areas, several hypotheses have 

been offered. One hypothesis states that the lighting on turbines attracts 

insects, which in turn attracts bats, but studies have not demonstrated 

differences in fatalities between lit turbines and unlit turbines. Other 

hypotheses include the notions that bats may be investigating wind 

turbines as potential roosting sites, that open spaces around turbines 

create favorable foraging habitats, and that migrating bats do not 

echolocate and thus are less able to avoid collision. One thing bat experts 

agree on is the need for more research.

In addition to these research gaps regarding bird and bat interactions with 

turbines, very little is known about bird and bat populations in general, 

such as their size and migratory pathways. An FWS official told us that data 

are available regarding the migration routes and habitat needs of only 

about one-third of the more than 800 bird species that live in or pass 

through the United States each year. In addition, bat researchers stressed 

to us that very little is known about the pathways and behavior of 

migratory bats. This lack of information, among other factors, makes it 

difficult to assess the cumulative impacts from wind power on species 

populations. One expert noted that many bird populations are in decline in 

general and additional losses due to wind power may exacerbate this trend. 

However, it is very difficult to attribute a decline in bird populations to 

wind power specifically or to get good data on overall populations that 

span international borders. Our literature search was only able to find one 

study in the United States that examined the impact of fatalities from wind 

power on a particular species population—golden eagles—and those 

results have been described as relatively inconclusive, or mixed, by other 

scientists. Without this kind of information, it can be difficult to determine 

the appropriate public policy responses to wildlife impacts due to wind 

power. 
Page 19 GAO-05-906 Wind Power

Although there are currently several gaps in the study of wind power’s 

direct impacts on birds and bats, FWS and the U.S. Geological Survey have 

recently initiated a study of bird and bat migration behaviors to address 

some of these data gaps. This study will use radar technology to 

characterize daily and seasonal movements and habitat and landform 

associations of migrating birds and bats, and will seek to develop decision 

support tools to provide assistance in identifying locations for wind 

turbines and communication towers. In addition, Congress has 

appropriated funds for a National Academy of Sciences study on the 

environmental impacts of wind power development in the Mid-Atlantic 

Highlands that will include developing criteria for the siting of wind 

turbines in this area. Finally, the Bats and Wind Energy Cooperative, a 

partnership of Bat Conservation International, the American Wind Energy 

Association, FWS, and the National Renewable Energy Laboratory, 

continues to sponsor research on bats and wind turbines focusing on 

acoustic deterrence methods and pre- and postconstruction risk 

assessment at a planned wind farm in the Appalachian region.

Few Studies Have Been 

Conducted on Mitigation 

Measures

Overall, there is much to be learned about mitigation strategies for 

reducing impacts from wind power facilities on birds and bats, and some 

strategies that once looked promising are now proving ineffective. 

Specifically, we found that relatively few studies have examined strategies 

for reducing the potential impacts of wind power on birds and bats. Some 

of these studies were based on information collected from birds in a 

laboratory setting, and, therefore, their conclusions still need to be verified 

by conducting studies at actual wind power facilities. One study examined 

the idea of addressing motion smear—the inability of birds to see moving 

blades—by painting turbine blades to make them more visible. This study 

indicated that color contrast was a critical variable in helping birds to see 

objects like moving turbine blades and recommended painting stripes on 

blades as a way to test whether this could be an effective deterrent. Some 

developers adopted this strategy; however, a recent study found that 

turbines with painted blades were ineffective in reducing bird kills. 

Another laboratory-based study tested bird reactions to noise and sound 

pressure and suggested that whistles could make blades more audible to 

birds, while making no measurable contribution to overall noise levels. 

However, the authors of this study made no predictions about changes in 

bird flight in response to hearing the noise and noted that field tests would 

be required to test this hypothesis. 
Page 20 GAO-05-906 Wind Power

Although there have been relatively few laboratory-based experiments on 

mitigation strategies, some strategies have already been attempted in 

Altamont Pass. A recent 4-year study conducted by the California Energy 

Commission in Altamont Pass tested some of these mitigation efforts 

attempted by industry and suggested possible future mitigation strategies. 

This study found that some of the strategies adopted by industry, such as 

perch guards on turbines and rodent control programs that reduce prey 

availability, were ineffective in reducing kills. Another study compared the 

differences between turbines painted with ultraviolet reflectant or 

nonultraviolet reflectant to see whether one would act as a visual 

deterrent, but the study found no evidence of a difference in mortality 

between the two treatments.

While there is less than adequate information on the effectiveness of 

mitigation strategies from existing scientific research, the experts with 

whom we spoke were hopeful about several strategies on the basis of their 

experience in the field. Some of these experts noted that because birds 

have been found to collide with electrical wires, wind facilities should bury 

their transmission lines under ground and avoid using guywires on their 

meteorological towers; such fixes have generally been adopted. Although 

some studies have shown that there are no differences in mortality rates for 

lit turbines versus unlit turbines, some experts argue that, regardless, it is 

best to use low lighting to avoid attracting birds that migrate at night. In 

addition, researchers recommended that sodium vapor lights should never 

be used at or near wind power facilities because they have commonly been 

shown to attract birds to other structures. They noted that the largest 

number of birds killed at one time near wind turbines was found adjacent 

to sodium lights after a night of dense fog. No fatalities have been 

discovered near these turbines since the lights were subsequently turned 

off. Some researchers have observed that many bird and bat kills occur 

during the time of year that has the lowest wind production. For example, 

most bats are killed during the fall migration season on low wind nights. 

Consequently, researchers suggested turning off some turbines during 

these times in order to reduce kills. Perhaps most importantly, many 

experts have noted that using preconstruction studies on wildlife and their 

habitats can help identify locations for wind turbines that are less likely to 

have adverse impacts.
Page 21 GAO-05-906 Wind Power

Regulating Wind Power 

Facilities on 

Nonfederal Land Is 

Largely the 

Responsibility of State 

and Local 

Governments 

Since most wind power development has occurred on nonfederal land, 

regulating wind power facilities is largely a state and local government 

responsibility. In the six states we reviewed, wind power development is 

subject to local-level processes, state-level processes, or a combination of 

the two. For example, in three of the six states, local governments regulate 

the development of wind power and generally require wind developers to 

adhere to local zoning ordinances and to obtain special use permits before 

construction. The federal role in regulating wind power development is 

limited to projects occurring on federal lands or those that have some form 

of federal involvement, such as projects that receive federal funding; to 

date, there have been relatively few wind power projects on federal land. In 

these cases, wind power projects must comply with federal laws as well as 

any relevant state and local laws.

State and/or Local 

Governments Regulate Wind 

Power on Nonfederal Lands 

State and/or local governments regulate the development and operation of 

wind power facilities on nonfederal lands. The primary permitting 

jurisdiction for wind power facilities in many states is a local planning 

commission, zoning board, city council, or county board of supervisors or 

commissioners. Typically, these local jurisdictional entities regulate wind 

projects under zoning ordinances and building codes. In some states, one 

or more state agencies play a role in regulating wind power development, 

such as natural resource and environmental protection agencies, state 

historic preservation offices, industrial development and regulation 

agencies, public utility commissions, or siting boards. In addition, some 

states have environmental laws that impose requirements on many types of 

construction and development, including wind power, that state and local 

agencies must follow. The regulatory scheme for wind power in the six 

states we reviewed included all of these scenarios (see table 1).
Page 22 GAO-05-906 Wind Power

Table 1: Type of Regulatory Process and Responsible Agency in Select States

Source: GAO analysis of state and local data.

In the six states we reviewed, we found that approval for the construction 

and operation of a wind power facility is typically provided in permits that 

are often referred to as site, special use, or conditional use permits or 

certificates. Such permits often include various requirements, such as 

“setback” provisions—which stipulate how far wind power turbines must 

be from other structures, such as roads and residences—and 

decommissioning requirements that are intended to ensure that once a 

wind power facility ceases operation, its structures are removed and the 

landscape is restored according to a specific standard. State and local 

regulations may require postconstruction monitoring studies to assess a 

facility’s impact on the environment. In one state we reviewed, facilities are 

required to submit periodic reports on issues related to its operation and 

impact on the surrounding area. 

In most of the six states we reviewed, state and local regulations related to 

wind power are evolving as the industry has developed in the states 

because government agencies realized that their existing authorities were 

not applicable to wind power. For example, when wind power began to 

emerge in Minnesota, an advisory task force held public meetings to 

determine how to proceed in permitting development. In part based on 

concerns raised from counties during these meetings, responsibility for 

permitting larger facilities was given to the state. In addition, West Virginia 

finalized new regulations for electric-generating facilities in May 2005 that 

include provisions specific to wind power facilities. Prior to this, the state 

made decisions on a case-by-case basis. Similarly, the Pennsylvania Game 

State

State/Local 

processes Regulatory agency/authority

California Local-only Local governments (are subject to the state’s environmental quality act, which 

requires assessment of environmental impacts of proposed actions)

Minnesota State and local Local governments regulate facilities under 5 megawatts, Minnesota Public Utility 

Commission regulates facilities 5 megawatts or larger

New York Local-only Local governments (are subject to the state’s environmental quality review act, which 

requires assessment of environmental impacts of proposed actions)

Oregon State and local Local governments regulate facilities under 105 megawatts (peak capacity), Oregon 

Energy Facility Siting Council regulates facilities 105 megawatts or larger

Pennsylvania Local-only Local governments

West Virginia State-only Public Service Commission (though local authorities could have some regulatory 

impact through zoning and subsidies)
Page 23 GAO-05-906 Wind Power

Commission is developing a policy for wind power development on its 

lands in response to private interest in promoting renewable energy 

sources on state property. Officials with the state’s Department of 

Environmental Protection also told us that they are examining a number of 

options, including developing statewide rules and model ordinances that 

could be adopted by local authorities. 

Some state and local regulatory agencies we reviewed generally had little 

experience or expertise in addressing environmental and wildlife impacts 

from wind power. For example, officials in West Virginia told us that they 

did not have the expertise to evaluate wildlife impacts and review studies 

prior to construction, although such studies are required. Instead, they said 

they rely on the public comment period while permits are pending for 

concerns to be identified by others, such as FWS and the state Division of 

Natural Resources. In addition, Alameda County officials in California told 

us that they did not have the expertise to assess the impacts of wind facility 

construction but rely on technical consultants during the permitting stage, 

and that they are planning to form a technical advisory committee for 

assistance with postapproval monitoring. In some of the states we 

reviewed, state agencies were conducting outreach efforts with local 

governments since wind power development is still a relatively new 

industry for regulators. These efforts typically focus on educating local 

regulators about the issues that are often encountered during wind power 

development and about how permitting can be handled. These efforts may 

also include providing sample zoning ordinances and permits. 

California California had the most installed wind power in the country, with 2,096 MW 

of generating capacity as of April 2005 and an additional planned capacity 

of 365 MW. California was the first state in which large wind farms were 

developed, beginning in the early 1980s. It is also one of the few states with 

significant wind power development on federal land, with over 250 MW on 

land owned by the Bureau of Land Management (BLM). Aside from the 

facilities on BLM land, the state relies on local governments to regulate 

wind power. In addition to the local permitting process, the California 

Environmental Quality Act requires all state and local government agencies 

to assess the environmental impacts of proposed actions they undertake or 

permit.12 This law requires agencies to identify significant environmental 

effects of a proposed action and either avoid or mitigate significant 

environmental effects, where feasible. 

12California Environmental Quality Act, Cal. Pub. Res. Code § 21100. 
Page 24 GAO-05-906 Wind Power

We met with officials from Alameda County and Contra Costa County, 

which are home to the Altamont Pass Wind Resource Area—at one time the 

largest wind energy facility in the world. In both counties, local land use 

ordinances allow wind power development on agricultural lands. These 

counties originally issued conditional or land use permits to various wind 

power developers in the 1980s that contained approval conditions, 

including requirements for setbacks from property lines and noise limits. 

As previously discussed, the Altamont Pass Wind Resource Area was 

subsequently found to be responsible for the deaths of numerous raptor 

species. The counties are currently renewing or amending some of the 

permits for facilities in this area and will add permit conditions in an 

attempt to reduce avian mortality. Alameda County officials were working 

with various federal and state agencies, environmental groups, and wind 

energy companies to agree on specific permit conditions. At the time of this 

report, Alameda County has recently approved a plan that is aimed at 

reducing bird deaths at Altamont Pass by removing some existing turbines, 

turning off selected turbines at certain times, implementing other habitat 

modification and compensations measures, and gradually replacing 

existing turbines with newer turbines. In addition, Contra Costa County 

had completed the permitting for a wind power facility that included a 

number of conditions to reduce avian mortality.

Minnesota Minnesota had 615 MW of installed wind generating capacity as of April 

2005 and an additional planned capacity of 213 MW. Wind power 

development in Minnesota is subject to either local or state permitting 

procedures, depending on the size of the project. Local governments 

generally issue conditional use permits or building permits to wind power 

developers for facilities under 5 MW. We spoke with officials in Pipestone 

County, which was the first in the state to adopt a wind power ordinance. 

This ordinance focuses mainly on setbacks and decommissioning 

requirements. In southwestern Minnesota—which includes Pipestone 

County and most of the wind power development in the state—a 14-county 

renewable energy board is working to adopt a “model” wind power 

permitting ordinance that would provide uniformity for regulating 

development in the region. Two factors that officials cited in pursuing such 

guidance is the recognition that development is likely to occur under the 5 

MW threshold for state permitting, and that wind power developers would 

benefit from uniform regulations. 

Between 1995 and the first half of 2005, the Minnesota Environmental 

Quality Board—comprised of 1 representative from the governor’s office, 5 

citizens, and the heads of 10 state agencies—was responsible for regulating 
Page 25 GAO-05-906 Wind Power

large wind energy systems that are 5 MW or larger, studying environmental 

issues, and ensuring state agency compliance with state environmental 

policy.13 Effective July 1, 2005, authority for permitting these large wind 

energy systems was transferred to the Minnesota Public Utilities 

Commission. The commission requires, among other things, an analysis of 

the proposed facility’s potential environmental and wildlife impacts, 

proposed mitigative measures, and any adverse environmental effects that 

cannot be avoided. Instead of requiring individual wind developers to 

conduct their own assessments of impacts to wildlife, Minnesota took a 

different approach. Since much of the wind power development is 

concentrated in the southwestern part of the state, the state determined 

that it would be more efficient to conduct one large-scale study, rather than 

requiring each developer to conduct individual studies. Thus, the state 

required wind developers to participate in a 4-year avian impact study at a 

cost of about $800,000 as well as a subsequent 2-year bat study. The studies 

concluded that the impacts to birds and bats from wind power are minimal. 

Therefore, on the basis of the results of the state-required studies, state and 

local agencies in Minnesota are not requiring postconstruction studies for 

wind power development in this portion of the state. The costs for these 

studies were charged back to individual wind developers on the basis of the 

number of megawatts built or permitted within a specified time frame. 

New York New York had three operating wind power facilities, with 49 MW of 

installed wind generating capacity as of April 2005. An additional 350 MW 

of wind power capacity is planned for the state. According to state officials, 

local governments permit the development of wind power in the state using 

their zoning authorities. In addition to this local permitting, the state has an 

environmental quality review act that requires all state and local 

government agencies to assess the environmental impacts of proposed 

actions, including issuing permits to wind power facilities.14 This law 

requires that an environmental impact statement be conducted if a 

proposed action is determined to have a potentially significant adverse 

environmental impact. Because wind power is still new to the state and 

there are a significant number of proposed facilities, a state agency focused 

on promoting energy development is beginning a program for educating 

local communities about regulating wind power. This program includes 

examples of zoning ordinances that have been used in other counties.

13Minn. Stat. §§ 116C.691 - 116C.697.

14State Environmental Quality Review Act, N.Y. Envtl. Conserv. Law § 8-0109. 
Page 26 GAO-05-906 Wind Power

We met with officials from the Town of Fenner—in north-central New 

York—which has the largest wind power facility in the state. On the basis 

of complaints about noise from the first facility permitted by the town, the 

local planning board now requires that turbines be located a certain 

distance from residences. In order to comply with the state’s environmental 

law, the town conducted an environmental assessment to determine the 

potential impacts of the proposed facility and determined that the project 

would not have any significant adverse environmental impacts or pose a 

significant risk to birds. However, elsewhere in New York, approval of one 

wind power project is under review given concerns expressed by 

environmental groups and the state environmental and conservation 

agency about potential impacts to migratory birds.

Oregon Oregon had five large wind projects, with a total of 263 MW of installed 

wind power generating capacity as of April 2005 (see fig. 5). 
Page 27 GAO-05-906 Wind Power

Figure 5: Wind Power Facility in Sherman County, Oregon

Several new wind projects and expansions are under way or being planned 

that would take total capacity in Oregon to more than 700 MW. Similar to 

Minnesota, wind power regulation in Oregon is subject to either local or 

state permitting procedures, depending on the size of the project. Local 

governments issue conditional use permits for facilities capable of 

generating up to 105 MW peak capacity. For example, in Sherman County, 

the planning commission approved a 24 MW wind power project near 

Klondike in north-central Oregon. Under its zoning authority, the county 

attached various conditions to the project’s permit, including an avian 

postconstruction study, and decommissioning and removal requirements. If 

projects exceed 105 MW peak capacity, they are permitted by the Oregon 

Energy Facility Siting Council, which makes decisions about issuing site 

certificates for energy facilities. The siting council is a seven-member 

citizen commission that is appointed by the governor. Wind power projects 

Source: GAO.

Wind turbine blade prior to being installed at expansion of the facility in Sherman County (left) 

and the wind power facility in Sherman County (right).
Page 28 GAO-05-906 Wind Power

that are subject to the council’s jurisdiction must comply with the council’s 

standards and applicable statutes. Some of the standards are specific to 

wind power, such as design and construction requirements to reduce visual 

and environmental impacts.15 The council also ensures that wind power 

facilities are constructed and operated in a manner consistent with state 

rules, such as state fish and wildlife habitat mitigation goals and standards, 

and local agency ordinances. In addition, regulations protect against 

impacts on the surrounding community by requiring that minimal lighting 

be used to reduce visual impacts, and protect some bird species by 

requiring that developers avoid creating artificial habitat for raptors or 

raptor prey. Also in Oregon, energy development—including wind 

power—must not adversely impact scenic and aesthetic values and is 

prohibited in certain areas, such as state parks. 

Pennsylvania Pennsylvania had 129 MW of installed wind generating capacity as of April 

2005 and applications for an additional 145 MW to be developed (see fig. 6). 

Figure 6: Wind Power Facility in Somerset County, Pennsylvania

15Oregon Revised Statutes (ORS) § 469.300 et seq.; Oregon Administrative Rules (OAR) 

Chapter 345, Divisions 1, 15, 20-23, 26, 27, and 29. 

Source: GAO.
Page 29 GAO-05-906 Wind Power

In Pennsylvania, wind power is regulated by local governments; no state 

agency has the authority to specifically regulate wind power development. 

For example, in Somerset County, which is home to the first wind power 

facility in the state, the county’s planning commission regulates wind 

power development through an ordinance that allows for subdividing 

existing land. This ordinance contains requirements for setbacks and 

decommissioning. Some county and state officials have suggested that the 

state should provide a consistent framework for wind power development. 

The state, through its Pennsylvania Wind Working Group, is currently 

discussing whether there should be uniform state-level siting guidelines or 

regulations for wind power development. Pennsylvania was the only state 

of the six we reviewed that did not have state-level requirements for 

environmental assessments. However, one state official told us that many 

developers have done some environmental studies—generally including 

wildlife, noise, and protection of scenic vistas (i.e., viewshed)—in an 

attempt to head off criticism or opposition to a proposed project.

West Virginia West Virginia had one operating wind power facility, with 66 MW of 

installed wind power generating capacity and a planned additional capacity 

of 300 MW for the state (see fig. 7). The state’s Public Service Commission 

has been the only agency involved in regulating wind power to date, 

although state officials noted that local governments could get involved 

through their zoning authorities. Prior to 2005, West Virginia permitted 

construction and operation of wind power facilities under laws and 

regulations designed to regulate utilities providing electrical service 

directly to its citizens. Wind power facilities are wholesale generators and 

do not provide service to consumers, and according to commission 

officials, several provisions of these regulations were not relevant to wind 

power facilities. As a result, in 2003, the state amended the legislation to 

specifically address the permitting of wholesale electric generators, such 

as wind power. 
Page 30 GAO-05-906 Wind Power

Figure 7: Wind Power Facility in Tucker County, West Virginia

West Virginia followed the regulations in place before the legislation was 

amended to approve construction of the two wind power facilities in the 

state; one of these facilities has yet to be constructed. During the public 

comment periods for these facilities, concerns were raised regarding 

potential impacts to wildlife. As a result, certain conditions were required 

of the developers, such as prohibiting turbines in certain locations and 

Source: GAO.
Page 31 GAO-05-906 Wind Power

requiring postconstruction wildlife studies.16 In May 2005, the state 

finalized new regulations for wholesale electric-generating facilities that 

include provisions specific to wind power facilities.17 For permitting wind 

power facilities, West Virginia regulations now require spring and fall avian 

migration studies, avian and bat risk assessments, and avian and bat 

lighting studies.

Federal Government’s Role 

in Regulating Wind Power Is 

Generally Limited to 

Facilities on Federal Land

The federal government’s role in regulating wind power development is 

limited to projects occurring on federal lands or projects that have some 

form of federal involvement. While the Federal Energy Regulatory 

Commission regulates the interstate transmission of electricity, natural gas, 

and oil, it does not approve the physical construction of electric generation, 

transmission, or distribution facilities; such approval is left for state and 

local governments. Certain standards issued by the Federal Aviation 

Administration apply to wind power facilities and other tall structures, on 

all lands. These standards are intended to protect aircraft and specify the 

type of lighting that should be used for structures of a certain height. 

Since the majority of wind development to date has been on nonfederal 

land or has not required federal funding or permits, the federal government 

has had a limited role in regulating wind power facilities. In those cases 

where federal agencies do regulate wind power, projects must comply both 

with state and local requirements and with any applicable federal law. At a 

minimum, these laws will include the National Environmental Policy Act 

and the Endangered Species Act.18 These laws often require 

preconstruction studies or analyses of proposed projects, and possibly 

project modifications to avoid adverse environmental effects. For example, 

if the development of a proposed wind power project on federal land could 

impact wildlife habitat and/or species protected under the Endangered 

Species Act, permitting of the project would involve coordination and 

consultation with FWS and/or the National Marine Fisheries Service to 

16Developers of these two facilities voluntarily conducted some preconstruction wildlife 

studies.

17The West Virginia Public Service Commission adopted Rules Governing Siting 

Certificates for Exempt Wholesale Generators (WV 150 C.S.R. 30) on May 25, 2005, effective 

July 25, 2005.

18Other federal laws may apply to wind power development on federal land, such as the 

Federal Land Policy and Management Act, which provides BLM with a framework for 

managing its land. 
Page 32 GAO-05-906 Wind Power

determine the potential harm to species and the steps that may be 

necessary to avoid or offset the harm. 

To date, BLM has been the only federal agency with wind energy 

production, with about 500 MW of installed wind power capacity.19 This 

wind energy development is located in Southern California in the San 

Gorgonio Pass and Tehachapi Pass areas, and in the Foote Creek Rim and 

Simpson Ridge areas of Wyoming.20 According to BLM officials, as of June 

2005, they had authorized 88 applications for wind energy development on 

their land and had 68 pending applications—most of which are in California 

and Nevada. Energy development on BLM-administered lands is regulated 

through its process for granting private parties access to federal lands, 

which is referred to as granting a “right-of-way authorization.” BLM’s 

Interim Wind Energy Development Policy establishes the requirements for 

granting these authorizations to wind energy facilities. This policy requires 

that all proposed facilities conduct the necessary assessments and analyses 

required by the National Environmental Policy Act, the Endangered 

Species Act, and other appropriate laws. In one case, some changes have 

been made to the location of some wind power turbines because of 

potential impacts to avian species that were identified during these 

preconstruction studies. 

Because of an increased focus on developing energy sources on public 

lands, BLM has proposed revising their interim policy by developing a wind 

energy development program that would establish comprehensive policies 

and best management practices for addressing wind energy development. 

As a part of this effort, BLM issued a programmatic environmental impact 

statement in June 2005 that assesses the social, environmental, and 

economic impacts of wind power development on BLM land. This 

document also identifies best management practices for ensuring that the 

impacts of wind energy development on BLM lands are kept to a minimum. 

While subsequent proposed wind power facilities will still need to conduct 

some environmental assessments, they can rely on BLM’s programmatic 

assessment for much of the needed analyses. BLM hopes that the 

availability of this assessment will enable wind power development to 

19At the time of this report, a developer had submitted an application to build what would be 

the first wind power project on U.S. Forest Service land.

20Postconstruction wildlife studies in these areas of California and Wyoming found low 

avian mortality. The California study in Tehachapi Pass was not included in appendix II 

because estimating fatality rates was not a primary goal of that study. 
Page 33 GAO-05-906 Wind Power

proceed more quickly on its lands, assuming that such development 

complies with needed requirements. 

Federal and State Laws 

Protect Wildlife 

As with any other activity, federal and state laws afford protections to 

wildlife from wind power. Three federal laws—the Migratory Bird Treaty 

Act, the Bald and Golden Eagle Protection Act, and the Endangered 

Species Act—generally forbid harm to various species of wildlife. While 

each of the laws allows some exceptions to this, only the Endangered 

Species Act includes provisions that would permit a wind power facility to 

kill a protected species under certain circumstances. While wildlife 

mortality events have occurred at wind power facilities, the federal 

government has not prosecuted any cases against wind power companies 

under these wildlife laws, preferring instead to encourage companies to 

take mitigation steps to avoid future harm. Regarding state wildlife 

protections, all of the six states we reviewed had statutes that can be used 

to protect some wildlife from wind power impacts. However, similar to 

FWS, no states have taken any prosecutorial actions against wind power 

facilities where mortalities have occurred. 

Various Wildlife Protections 

Are Provided by Three 

Federal Laws

The primary federal regulatory framework for protecting wildlife from 

impacts from wind power includes three laws—the Migratory Bird Treaty 

Act, the Bald and Golden Eagle Protection Act, and the Endangered 

Species Act. (See table 2.)
Page 34 GAO-05-906 Wind Power

Table 2: Federal Wildlife Protection Laws 

Source: GAO analysis of federal laws.

FWS is primarily responsible for ensuring the implementation and 

enforcement of these laws.21 In general, these laws prohibit various actions 

that are deemed harmful to certain species. For example, each law 

prohibits killing or “taking” a protected species, unless done under 

circumstances that are expressly allowed by statute and authorized via 

issuance of a federal permit. The Endangered Species Act may also prohibit 

actions that harm a protected species’ habitat. In addition, each federal 

agency that takes actions that have or are likely to have negative impacts 

on migratory bird populations are directed by Executive Order 13186, 

“Responsibilities of Federal Agencies to Protect Migratory Birds,” to work 

with FWS to develop memorandums of understanding to conserve those 

species. While the executive order was signed on January 10, 2001, no 

memorandums have yet been signed. Wildlife species that fall outside the 

Federal wildlife law Protections Permits Penalties for violations

Migratory Bird Treaty 

Act

Prohibits the taking, killing, possession, 

transportation, and importation of over 

860 migratory birds, their eggs, parts, 

and nests, except when specifically 

authorized by FWS 

Authorizes permits for some 

activities, including but not limited 

to, scientific collecting, depredation, 

propagation, and falconry

No permit provisions for “incidental 

take”

Only criminal penalties are 

possible, with violators subject 

to fine and/or imprisonment

Bald and Golden 

Eagle Protection Act

Prohibits the taking and sale of bald and 

golden eagles and their eggs, parts, and 

nests, except when specifically 

authorized by FWS 

Authorizes permits for scientific or 

exhibition purposes, or religious 

purposes by Indian tribes; and for 

other purposes

No permit provisions for “incidental 

take”

Civil and criminal penalties are 

possible, with violators subject 

to civil penalties, fines, and/or 

imprisonment

Endangered Species 

Act

Protects about 1,265 species that have 

been determined to be at risk for 

extinction, referred to as threatened or 

endangered species; prohibits the taking 

of protected animal species, including 

actions that “harm” or “harass”; federal 

actions may not jeopardize listed species 

or adversely modify habitat designated 

as critical

Authorizes permits for the “taking” 

of protected species if the permitted 

activity is for scientific purposes, is 

to establish experimental 

populations, or is incidental to an 

otherwise legal activity, such as 

construction of wind turbines 

Civil and criminal penalties are 

possible, with violators subject 

to civil penalties, fines, and/or 

imprisonment 

21FWS shares responsibility for enforcing the Endangered Species Act with the National 

Marine Fisheries Service, which is responsible for protecting ocean-dwelling species and 

anadromous species, such as salmon.
Page 35 GAO-05-906 Wind Power

scope of these three laws, such as many species of bats, are generally not 

protected under federal law. However, FWS is not only responsible for 

ensuring the survival of species protected by specific laws, but also for 

conserving and protecting all wildlife. 

All three of the federal wildlife protection laws prohibit most instances of 

“take,” although each law provides for some exceptions, such as scientific 

purposes. The Endangered Species Act is the least restrictive of these laws 

in that it authorizes FWS to permit some activities that take a protected 

species as long as the take meets several requirements, including a 

requirement that the take be incidental to an otherwise legal activity. Wind 

power facilities may seek an incidental take permit under this act for 

facilities sited on private land or where no federal funding is used or federal 

permit is required. The Migratory Bird Treaty Act and the Bald and Golden 

Eagle Protection Act also allow permits for take, but incidental take of 

migratory birds is not allowed. Under all three statutes, unauthorized 

takings may be penalized, even if the offender had no intent to harm a 

protected species.22

Although not required by these federal laws, in some cases, state or local 

entities that regulate wind power, or wind power developers themselves, 

will consult with FWS for information on protected species or advice on 

how to ensure that wind power facilities will not harm wildlife. For 

example, in the Altamont Pass Wind Resource Area, Alameda County 

officials and the companies operating wind facilities there have asked FWS 

for technical assistance related to renewing permits for existing wind 

power facilities. FWS officials told us that their technical assistance in 

Altamont Pass is aimed at avoiding or minimizing potential impacts to 

threatened or endangered species under the Endangered Species Act. In 

addition, FWS officials from the New York field office told us that they are 

asked to provide input on wind power proposals during the state’s 

environmental review process. These officials noted that they will likely 

not be able to review all of the wind power development proposals in the 

state due to staffing constraints. Similarly, FWS officials in five of the six 

states we reviewed told us that they have not conducted outreach to state 

or local regulators to inform them of the potential for wildlife impacts from 

wind power primarily because of workload constraints. If state and local 

regulators do not consult with FWS during the regulatory process, it can be 

22FWS identifies violations of federal wildlife laws in several ways, including by receiving 

citizen complaints and self-reporting by industry or individuals. 
Page 36 GAO-05-906 Wind Power

difficult for FWS to encourage actions that might reduce wildlife deaths 

before wind turbines are sited. 

Federal Government Uses 

Prosecutorial Discretion in 

Dealing with Wildlife 

Mortality 

Although FWS investigates all “take” of federal trust species, the 

government has elected not to prosecute wind energy companies for 

violations of wildlife laws at this time. In most of the states we reviewed, 

there were relatively few law enforcement officials, and they told us that 

they often had higher priority violations of federal wildlife laws than 

mortality events due to wind power, particularly given the relatively low 

levels of mortality that have occurred in most wind power locations. In 

West Virginia, the agent-in-charge told us that most of his time is spent on 

the commercialization of wildlife, such as the illegal import and export and 

interstate commerce of protected species; illegal hunting is also a major 

problem, particularly for bears and eagles. FWS law enforcement officials 

in all of the six states we reviewed told us that in cases of violations, they 

prefer to work cooperatively with the owners of wind power facilities to try 

to get them to take voluntary actions to address impacts on wildlife, rather 

than pursuing prosecution; however, other cases of wildlife violations, such 

as illegal trade in protected species, are pursued via prosecution. 

FWS has been investigating and monitoring avian mortality at Altamont 

Pass for nearly 20 years, including the mortality of many protected species, 

such as golden eagles and other raptors.23 Since that time, FWS has opened 

investigations and tried to work with the owners of wind power facilities to 

reduce the level of mortality. In the earlier years, some avian mortality was 

due to electrocutions along power lines. FWS had been working with 

electrical utility companies to resolve this problem elsewhere, and several 

relatively easy “fixes” were known to reduce electrocutions. As a result of 

official correspondence and conversations between FWS and company 

officials, many companies implemented these fixes, and avian mortality 

due to electrocutions has been reduced. However, large numbers of birds, 

particularly raptors, were still being killed due to actual collisions with 

wind turbines. On several occasions, FWS expressed concern about these 

mortalities to wind power companies and Alameda County—the county 

government with the most wind power development in California. In 

response, Alameda County and some wind power companies have 

conducted avian monitoring studies and tested several mitigation 

23Of all the species that have been killed, only two endangered species kills have been 

documented—a peregrine falcon in 1996 and a brown pelican in 2002.
Page 37 GAO-05-906 Wind Power

measures, including painting turbine blades, installing perch guards on 

lattice-work towers, and conducting rodent control. However, these 

actions appear to have no significant impact on reducing avian mortality. 

Since January 2004, the wind power companies have worked together to 

develop an adaptive management plan for reducing avian mortality at 

Altamont Pass. The plan contains various mitigation measures, such as 

(1) removing old turbines and replacing them with fewer, new turbines and 

(2) implementing a partial seasonal shutdown of turbines. 

Over the past 6 years, FWS has referred about 50 instances of golden eagles 

killed by 30 different companies in Altamont Pass either to the Interior 

Solicitor’s office for civil prosecution or to the Department of Justice for 

criminal prosecution. Officials noted that, in general, prosecutions by both 

the Departments of the Interior and Justice focus on companies that kill 

birds with disregard for their actions and the law, especially when 

conservation measures are available but have not been implemented. 

Despite the recurring nature of the avian mortality in Altamont Pass and 

concerns from federal, state, and local officials, no prosecutions pursuant 

to federal wildlife laws have been taken against any wind power 

companies. Justice has not pursued prosecution in these cases, although 

they currently have an open investigation on avian mortality in Altamont 

Pass. As a matter of policy, Justice does not discuss the reasons behind 

specific case declinations, nor does it typically confirm or deny the 

existence of potential or actual investigations. However, Justice officials 

told us that, in general, when deciding to prosecute a case criminally, they 

consider a number of factors, including the history of civil or 

administrative enforcement, the evidence of criminal intent, and what steps 

have been taken to avoid future violations. Regarding the matters that FWS 

referred for civil enforcement, Interior’s regional solicitor has also not 

pursued prosecution in any of these cases. Interior’s Office of the Solicitor 

San Francisco field office declined to pursue the most recent civil referrals 

because Justice agreed to review turbine mortalities for possible criminal 

prosecution. Some citizen groups remain concerned about the lack of 

enforcement of federal and state wildlife protections. For example, in 

November 2004, the Center for Biological Diversity filed a lawsuit against 

the wind power companies in Altamont Pass to seek restitution for the 

killing of raptors.24

24Center for Biological Diversity v. FPL Group, No. RG04183113 (Calif. Super. Ct., Alameda 

County, filed Nov. 1, 2004).
Page 38 GAO-05-906 Wind Power

In addition to the avian mortalities at Altamont Pass, significant wildlife 

mortality has also occurred at wind power locations in the Appalachian 

Mountains in West Virginia and Pennsylvania in 2003 and 2004. FWS has 

reviewed high numbers of bat kills; however, these bat species are not 

protected under federal law. Several studies have been completed or are 

under way in these regions to better determine the potential causes of the 

mortality events and how future events might be mitigated. The FWS law 

enforcement agent-in-charge in West Virginia told us that he has contacted 

wind power developers of some of the proposed facilities in the state about 

potential violations of federal wildlife laws should an endangered bat or 

other protected species be killed. The agent said that he prefers to have 

early involvement with wind power facilities, rather than wait for violations 

to occur. 

FWS law enforcement officials told us that the way they have handled avian 

mortalities at wind power facilities is similar to how they deal with wildlife 

mortality caused by other industries. These officials explained that FWS 

recognizes that man-made structures will generally result in some level of 

unavoidable incidental take of wildlife and, as a result, FWS reserves a level 

of “enforcement discretion” in determining whether to pursue a violation of 

federal wildlife law. Law enforcement officials told us that before FWS 

pursues civil or criminal penalties, the agency prefers to work with a 

company to encourage them to take mitigation and conservation steps to 

avoid future harm. If a company shows a good-faith effort to reduce 

impacts, FWS will likely not refer such a case for prosecution. If, however, 

a company repeatedly refuses to take steps suggested by FWS, officials 

said they are likely to refer it for prosecution. 

Work that FWS has done with the electric power industry illustrates this 

approach to resolving impacts to wildlife. FWS began working with the 

electric power industry in the early 1980s to reduce significant avian 

mortality due to collisions with and electrocutions at power lines, 

particularly mortality events involving eagles and other large birds. 

Pursuant to investigations of avian mortality at power lines and 

conversations with individual companies, solutions were identified that 

reduced mortality events. Because these solutions were relatively 

inexpensive and generally easy to install based on scientific testing—and 

were known to work—FWS law enforcement officials expected other 

electric line companies to install them. According to law enforcement 

officials, the threat of a potential conviction under the Migratory Bird 

Treaty Act or the Bald and Golden Eagle Protection Act was generally 

enough to get companies to voluntarily install the fixes without FWS 
Page 39 GAO-05-906 Wind Power

prosecuting them. However, by the late 1980s, some electric companies 

were aware of mortalities due to electrocutions but were not taking actions 

to resolve the causes. The federal government in 1998 charged an electric 

utility cooperative—the Moon Lake Electric Association in Colorado and 

Utah—with criminal violations of these two laws. This is the first and only 

instance of a federal criminal prosecution of an electric power line 

company under any of the three federal wildlife protection laws. Civil cases 

have been filed and out-of-court agreements have been reached with other 

electric utilities for similar cases of wildlife mortalities. 

FWS Has Taken Some 

Proactive Steps to Help 

Minimize the Impacts of 

Wind Power on Wildlife

Even though FWS does generally not have a direct role in determining 

whether and how wind power facilities are permitted, FWS has been 

involved for about 20 years with the wind power industry to help avoid and 

minimize impacts to wildlife from wind power development. FWS’s work 

has been in the following three main areas—participating on a national 

wind working group and in technical workshops, and issuing guidance.

Working Group An FWS senior management official has been a member of the National 

Wind Coordinating Committee since 1997. The wildlife workgroup serves 

as an advisory group for national research on wind-avian issues and a 

forum for defining, discussing, and addressing wind power-wildlife 

interaction issues. The workgroup has facilitated five national avian-wind 

power planning workshops to define needed research and explore current 

issues. The most recent workshop also included discussions of bat-wind 

turbine interactions. In addition, the working group released a report in 

December 1999, Studying Wind Energy/Bird Interaction: A Guidance 

Document, that includes metrics and methods for determining or 

monitoring potential impacts on birds at existing and proposed wind 

energy sites. 

Workshops FWS officials have participated in industry-sponsored workshops and 

conferences. For example, a senior FWS official presented information on 

cumulative impacts on wildlife from wind power at a 2004 workshop 

cosponsored by the American Wind Energy Association and the American 

Bird Conservancy. Another FWS official presented information on the 

agency’s experience and expectations for regional wildlife issues at a 

national workshop on wind power siting sponsored by the wind 

association. FWS also helped to sponsor and organize, and participated in, 

a 2004 bats and wind power technical workshop attended by both wind 

industry representatives and researchers. As a result, FWS was 
Page 40 GAO-05-906 Wind Power

instrumental in establishing the Bats and Wind Energy Cooperative 

discussed elsewhere in the report.

Guidance In July 2003, in an effort to inform wind power developers about the 

potential impacts to wildlife and encourage them to take mitigating actions 

before construction, FWS issued interim voluntary guidelines for industry 

to use in developing new projects. FWS developed the interim guidelines in 

response to the Department of the Interior’s push to expand renewable 

energy development on public lands. The wind power interim guidelines 

are intended to assist FWS staff in providing technical assistance to the 

wind energy industry to avoid or minimize impacts to wildlife and their 

habitats through (1) proper evaluation of potential wind energy 

development sites, (2) proper location and design of turbines, and (3) preand postconstruction research and monitoring to identify and assess 

impacts to wildlife. The voluntary guidelines were open for public 

comment for a 2-year period that ended on July 10, 2005. At the time of this 

report, FWS had received numerous comments from the wind industry on 

the guidelines. In general, industry representatives thought that the 

guidelines were overly restrictive—to a degree not supported by the 

relative risk that wind power development poses to wildlife compared with 

other sources of mortality. FWS also had received comments from other 

groups—such as the Ripley Hawk Watch, the Clean Energy States Alliance, 

the Humane Society of the United States, the Massachusetts and 

Pennsylvania Audubon, the American Bird Conservancy, Defenders of 

Wildlife, and Chautaqua County Environmental Management Council—that 

were generally in support of the guidance or recommended that it be put 

into regulation. BLM also provided comments and expressed some 

concerns over the review process outlined in the guidelines. FWS will be 

reviewing and incorporating the public, industry, and agency comments 

received on the interim guidelines as appropriate in order to revise and 

improve them, and will solicit additional public input before disseminating 

a final version.

In addition, FWS recently began developing a template for a letter to be 

sent to wind power project applicants to alert them to federal wildlife 

protection laws, FWS’s interim guidance, and FWS’s role in protecting 

wildlife. FWS officials told us that they hope the letter will assist 

developers in making informed decisions regarding site selection, project 

design, and compliance with applicable laws. The availability of a 

ready-to-use template is important because most field officials told us that 

working with the wind power industry is just one of many responsibilities 

in FWS offices that often do not have enough staff, given their workloads. 
Page 41 GAO-05-906 Wind Power

Field officials also noted that if wind power developers, their consultants, 

or state or local regulatory agencies do not contact them, they may not 

know about wind power projects until there is a problem with an operating 

facility. 

All Six States We Reviewed 

Have Wildlife Protections

Although federal jurisdiction for migratory birds has not been delegated to 

the states and primary responsibility for the protection of these birds 

resides with Interior, all states we reviewed had additional wildlife 

protections. Responsibility for protecting species and implementing 

wildlife laws and regulations is typically found in a state’s natural resource 

protection agency. In some states, however, responsibility is assigned 

according to the type of species addressed. For example, in some states, 

agriculture departments address plant issues, while in other states, fish and 

boat commissions address fish, amphibian, and reptile issues; in these 

cases, wildlife agencies typically address the remaining species. 

In all six states, the most common laws related to wildlife protection—and 

likely the most utilized wildlife laws—are those that govern hunting and 

fishing. These laws and regulations may include limits on the type and 

number of species that can be killed and the manner in which they can be 

taken. In addition to identifying the species that can be hunted or fished, 

the six states we reviewed identify as threatened or endangered specific 

species that are at risk for extinction or extirpation in their state. These 

states also identify “species of concern” or rare species. Such species are 

identified as a way to provide an early warning signal for species that are 

not yet endangered or threatened, but could become so in the future.

All of the six states we reviewed have laws that provide at least some 

degree of protection for species that are at risk of extinction or extirpation 

in their state. These protections generally go beyond what the federal 

Endangered Species Act provides by protecting more species than are 

protected under the federal law, although the protections may not be as 

extensive. In the five states that have specific protections, protection is 

provided through prohibitions on taking a protected species. In some 

cases, these protections are only applicable under certain circumstances. 

For example, in Oregon, protections apply only to state actions or on 

state-owned or -managed lands. All of the state laws or regulations that 

include take prohibitions, also include exceptions for when permits can be 

issued in order to allow the take to occur. Such permits are issued 

according to prescribed conditions or on a case-by-case basis. Two of the 

six states also provide protections for habitat. In West Virginia, the primary 
Page 42 GAO-05-906 Wind Power

protection for wildlife, aside from hunting and fishing regulations, is a 

prohibition on the commercial sale of wildlife and specific protection for 

bald and golden eagles. 

Most of the states’ wildlife protection laws for threatened and endangered 

species include enforcement provisions. In some cases, these laws identify 

violations as misdemeanor crimes. Similar to FWS law enforcement’s 

approach to wind power, we found that state agencies had not taken any 

prosecutorial actions in response to wildlife mortalities at wind power 

facilities. Instead, many state officials told us that they prefer—like 

FWS—to work with developers to try to identify solutions to the causes of 

mortality. For example, in Minnesota, after impacts to native prairie grass 

caused by a wind power facility were discovered, the state natural resource 

agency required the facility to purchase additional habitat elsewhere to 

compensate for the loss. In California, Alameda County has worked with 

wind power facilities and others, and recently approved a plan that is 

aimed at reducing bird deaths at Altamont Pass by having wind power 

companies turn off selected turbines at certain times and replace some 

turbines with newer turbines. 

State natural heritage programs serve as key sources of information on 

wildlife for federal and state wildlife protection agencies. All six of the 

states we reviewed have natural heritage programs that manage 

information on natural resources, including threatened and endangered 

species (all 50 states have such programs). These programs are part of an 

international effort to gather and share information on biological 

resources. This effort has slightly different designations and criteria for 

identifying imperiled species and habitat than the federal Endangered 

Species Act. In five of the states we reviewed, the natural heritage program 

is run by the states’ natural resource agencies; in the sixth state, Oregon, it 

is run by a university. Although West Virginia does not have a state 

endangered species law and protects only bald and golden eagles, it does 

identify other imperiled species through its natural heritage program.

State natural resource agencies—which typically house the natural 

heritage programs—are sometimes consulted by a state or local wind 

power regulator or a wind power developer during the permitting process 

for help in identifying potentially sensitive species or concerns about 

possible impacts to wildlife in general. For example, staff from West 

Virginia’s natural resources agency were involved in reviewing wildlife 

monitoring studies conducted by the first wind power facility in the state. 

During the consultation process on another proposed facility in the state, 
Page 43 GAO-05-906 Wind Power

agency staff requested that certain studies be conducted because of 

concerns about impacts on bat populations. Similarly, in Minnesota, natural 

resource agency staff requested changes in the location, construction, and 

operation of certain proposed wind power turbines through the state’s 

environmental review process. However, in some cases, the process for 

regulators or wind power developers to consult with natural resource 

agency staff on wildlife is often an informal one and is not necessarily 

required by states’ species protections or laws and regulations used to 

permit wind power. 

Conclusions In the context of other sources of avian mortalities, it does not appear that 

wind power is responsible for a significant number of bird deaths. While we 

do not know a lot about the relative impacts of bat mortality from wind 

power relative to other sources, significant bat mortality from wind power 

has occurred in Appalachia. However, much work remains before scientists 

have a clear understanding of the true impacts to wildlife from wind power. 

Scientists, in particular, are concerned about the potential cumulative 

impacts of wind power on species populations if the industry expands as 

expected. Such concerns may be well-founded because significant 

development is proposed in areas that contain large numbers of species or 

are believed to be migratory flyways. Concerns are compounded by the fact 

that the regulation of wind power varies from location-to-location and 

some state and local regulatory agencies we reviewed generally had little 

experience or expertise in addressing the environmental and wildlife 

impacts from wind power. In addition, given the relatively narrow 

regulatory scope of state and local agencies, it appears that when new wind 

power facilities are permitted, no one is considering the impacts of wind 

power on a regional or “ecosystem” scale—a scale that often spans 

governmental jurisdictions. FWS, in its responsibility for protecting 

wildlife, is the appropriate agency for such a task and in fact does monitor 

the status of species populations, to the extent possible. However, because 

wildlife, federally protected birds in particular, face a multitude of threats, 

many of which are better understood than wind power, FWS officials told 

us that they generally spend a very small portion of their time assessing the 

impacts from wind power. Nonetheless, FWS has taken some steps to reach 

out to the wind power industry by, among other things, issuing voluntary 

guidelines to encourage conservation and mitigation actions at new wind 

power facilities. In addition, FWS and the U.S. Geological Survey are 

initiating some studies to capture data on migratory flyways to help 

determine where the most potential harm from wind power might occur 

and to gather data for use in assessing wind power’s cumulative impacts on 
Page 44 GAO-05-906 Wind Power

species. Although these are valuable steps in educating industry and 

improving science, FWS has conducted only limited outreach to state and 

local regulators about minimizing impacts from wind power on wildlife and 

informing them about species that may be particularly vulnerable to 

impacts from wind power. Such outreach is important because these are 

the entities closest to the day-to-day decisions regarding where wind power 

will be allowed on nonfederal land.

Recommendations for 

Executive Action

Given the potential for future cumulative impacts to wildlife species due to 

wind power and the limited expertise or experience that local and state 

regulators may have in this area, we recommend that the Secretary of the 

Interior direct the Director of the FWS to develop consistent 

communication for state and local wind power regulators. This 

communication should alert regulators to (1) the potential wildlife impacts 

that can result from wind power development; (2) the various resources 

that are available to help them make decisions about permitting such 

facilities, including FWS state offices, states’ natural resource agencies, 

and FWS’s voluntary interim guidelines—and any subsequent 

revisions—on avoiding and minimizing wildlife impacts from wind 

turbines; and (3) any additional information that FWS deems appropriate.

Agency Comments and 

Our Evaluation

We provided copies of our draft report to the Department of the Interior 

and received written comments. (See app. III for the full text of the 

comments received and our responses.) Interior officials stated that they 

generally agree with our findings and our recommendation in the report. 

We also sent portions of the report to state and local regulators and state 

wildlife protection agencies. Many of these entities provided technical 

comments, which we incorporated as appropriate. Interior also provided 

technical comments, which we incorporated where appropriate.

Interior officials agreed in most part with our recommendation to develop 

consistent communication to deliver to state and local wind power 

regulators. However, they stated that because the comment period on the 

FWS voluntary interim guidelines has closed and final guidelines have yet 

to be developed, it would be inappropriate to include these in such 

communication. However, because FWS is currently disseminating the 

voluntary interim guidelines on wind power to its field offices to share with 

regulators and developers, we believe that it is appropriate to include 

reference to this document in communications to local and state 
Page 45 GAO-05-906 Wind Power

regulators. As Interior noted, these voluntary guidelines are currently 

undergoing review and revision. Therefore, it would be appropriate to draw 

attention to this fact in any such communication and to provide 

information about how the most current version might be accessed. 

As agreed with your offices, unless you publicly announce the contents of 

this report earlier, we plan no further distribution until 30 days from the 

report date. At that time, we will send copies of this report to the Secretary 

of the Interior, as well as to appropriate congressional committees and 

other interested Members of Congress. We also will make copies available 

to others upon request. In addition, the report will be available at no charge 

on the GAO Web site at http://www.gao.gov. 

If you or your staffs have questions about this report, please contact me at 

(202) 512-3841. Contact points for our Offices of Congressional Relations 

and Public Affairs may be found on the last page of this report. Key 

contributors to this report are listed in appendix IV.

Robin M. Nazzaro

Director, Natural Resources 

 and Environment
Page 46 GAO-05-906 Wind Power

Appendix I

Objectives, Scope, and Methodology ApApenednxidexiIs

On the basis of a June 22, 2004, request from the Ranking Democratic 

Members—House Resources Committee and the House Appropriations 

Subcommittee on Science, the Departments of State, Justice, and 

Commerce and Related Agencies—and of subsequent discussions with 

their staffs, we reviewed wind energy development and impacts on wildlife. 

Specifically, we assessed (1) what available studies and experts have 

reported about the impacts of wind power facilities on wildlife in the 

United States and what can be done to mitigate or prevent such impacts, 

(2) the roles and responsibilities of government agencies in regulating wind 

power facilities, and (3) the roles and responsibilities of government 

agencies in protecting wildlife from the risks posed by wind power 

facilities.

To determine what available studies and experts have reported about the 

direct impacts of wind power facilities on wildlife, we reviewed scientific 

studies and reports on the subject that were conducted by government 

agencies, industry, and academics. Our review focused on wildlife mortality 

as opposed to indirect impacts, which include habitat modification and 

disruption of feeding or breeding behaviors due to wind power facilities. 

We used several criteria to select studies for review. We chose studies that 

included original data analyses (rather than summaries of existing 

literature) conducted in the United States since 1990, and we primarily 

focused on the impact of wind power on birds and bats and/or ways in 

which to mitigate those impacts. We did not include preconstruction 

assessments of wildlife impacts in our review. We excluded studies that had 

preliminary findings when there was a more recent version available. We 

located studies using a database search with keywords of “wind power” 

and “birds,” “bats,” or “wildlife” in the following databases: AGRICOLA, 

DOE Information Bridge, National Environmental Publications 

Information, Energy Citations Database, Energy Research Abstracts, 

Environmental Sciences and Pollution Management, and JSTOR. In 

addition, we located studies using bibliographies of other studies and 

through publicly available lists of studies from the National Wind 

Coordinating Committee, the California Energy Commission, the National 

Renewable Energy Laboratory, and Bat Conservation International. We 

shared our list of studies with experts and asked them to identify any 

studies missing from our list. When studies were not publicly available, we 

contacted the authors and attempted to obtain copies. Using these methods 

and criteria, we obtained 31 studies. We reviewed the studies’ methodology, 

assumptions, limitations, and conclusions for the purposes of excluding
Appendix I

Objectives, Scope, and Methodology

Page 47 GAO-05-906 Wind Power

studies that did not ensure a minimal level of methodological rigor.1 We 

excluded 1 study, leaving 30 studies that are used in this work. In addition 

to these studies, we also reviewed two summaries of studies produced by 

the National Wind Coordinating Committee. Generally, we did not directly 

use these two summary studies, we did use them as a check for our 

conclusions and findings in relation to the studies we reviewed.2

 We also 

interviewed experts and study authors from the Department of the 

Interior’s U.S. Fish and Wildlife Service (FWS), state government agencies, 

academia, wind industry, and conservation groups and obtained their views 

on the risks of wind power facilities to migratory birds and other wildlife 

and on ways in which to minimize these risks. 

To determine the roles and responsibilities of government agencies in 

regulating wind power facilities, we identified and evaluated relevant 

federal laws and regulations for wind power development. We reviewed a 

nonprobability sample of six states with wind power development—

California, Minnesota, New York, Oregon, Pennsylvania, and West Virginia. 

We selected these states to reflect a range in installed capacity, different 

regulatory processes, a history of wind power development, and 

geographic distribution and to reflect our requesters’ interests. For these 

states, we identified and evaluated relevant state and local laws and 

regulations for wind power development. We interviewed federal officials 

from FWS, Bureau of Land Management, and Interior’s Office of the 

Solicitor as well as officials from the Department of Justice. We 

interviewed officials from FWS headquarters and from field office locations 

in the six states that we selected. We also interviewed officials from various 

state agencies, such as the Oregon State Siting Council and the West 

Virginia Public Service Commission, and from local and county 

governments that were responsible for issuing permits or certificates for 

the development of wind power facilities in their states. Finally, we visited 

wind power facilities in California, New York, Oregon, Pennsylvania, and 

West Virginia and interviewed wind industry company officials. 

To determine the roles and responsibilities of government agencies in 

protecting wildlife from the risks posed by wind power facilities, we 

identified and evaluated relevant federal, environmental, and wildlife 

1

Many of these studies have not been scientifically peer-reviewed, and the protocols in each 

study may vary.

2

We referenced one of these studies in two places in this report. In each of these places, a 

source and associated caveat are presented in a footnote.
Appendix I

Objectives, Scope, and Methodology

Page 48 GAO-05-906 Wind Power

protection laws and regulations. We interviewed FWS law enforcement 

officials from headquarters and the six states that we reviewed. For the six 

states that we selected, we identified and evaluated relevant state and local 

environmental and wildlife protection laws. We also interviewed officials 

from state environmental and wildlife agencies in California, Minnesota, 

New York, Oregon, Pennsylvania, and West Virginia. 

We conducted our work between December 2004 and July 2005 in 

accordance with generally accepted government auditing standards, 

including an assessment of data reliability and internal controls.
Page 49 GAO-05-906 Wind Power

Appendix II

Studies of Bird, Bat, and Raptor Fatality Rates, 

by Region ApendxiI

Table 3 includes only studies where calculating bird or bat mortality was a 

primary goal. Some studies may contain more than one study location.

Table 3: Studies of Bird, Bat, and Raptor Fatality Rates, by Region

Source: GAO analysis of various scientific studies and reports.

Notes: 

*** indicates that the study authors did not calculate a mortality rate for that category.

Some of the studies that presented a bird/turbine/year mortality rate also included raptors in that 

calculation. With the exception of the studies conducted in the Appalachian region, most of the studies 

listed were designed and timed to focus on bird mortality. Bats were found only incidentally to the study 

Fatalities per turbine, per year

Region Location and year

Number of

turbines Birds Bats Raptors

Pacific NW Stateline, OR - 2003 181 1.93 1.12 0.06

Nine Canyon, OR - 2003 37 3.59 3.21 0.07

Klondike, OR - Phase I - 2003 16 1.16a 1.16 0

Vansycle, OR - 2000 38 0.63 0.74 0

West Foote Creek Rim, WY - 2003 69 1.5 1.34 0.03

National Wind Tech Center, CO - 2003 Varies 0 0 0

California Altamont Pass, CA - (Thelander et al) - 2003 5,400 0.19` *** ***

Altamont Pass, CA - (CEC) - 2004 5,400 0.87 0.004 0.24

Altamont Pass and Solano County, CA - 1992 7,340 *** *** 0.058 (1989)

0.025 (1990)

Altamont Pass, CA - 1991 3,000 *** *** 0.047b

Montezuma Hills, CA - 1992 600 0.074b *** 0.047b

Midwest Buffalo Ridge, MN - P1 - 2000 73 0.98 0.26 ***

Buffalo Ridge, MN - P2 - 2000 143 2.27 1.78 ***

Buffalo Ridge, MN - P3 - 2000 138 4.45 2.04 ***

Buffalo Ridge, MN - (Osborn et al) - 2000 73 0.33-0.66 *** ***

Buffalo Ridge, MN - (Bats) - 2004 281 *** 3.02 (2001)

1.3 (2002)

***

Northeastern, WI - 2002 31 1.29 4.26 0

Top of Iowa - 2004 89 0.12c 1.88c ***

Northeast Searsburg, VT - 2002 11 0 *** 0

Appalachian Mt. 

Region

Mountaineer, WV - 2004 44 4.04d 47.53d ***

Tennessee - 2005 3 7.28 20.8 ***

Mountaineer, WV - 2005 44 *** 38.0e ***

Meyersdale, PA - 2005 20 *** 23.0e ***
Appendix II

Studies of Bird, Bat, and Raptor Fatality 

Rates, by Region

Page 50 GAO-05-906 Wind Power

objectives; therefore, rates of bat mortality reported from those studies may not represent a reliable 

measure.

a

Fatality rate applies to small birds only.

b

Fatality rate not adjusted for both searcher efficiency and scavenging rate.

c

Fatality rate represents number of birds and bats killed per turbine per 8-month study period.

d

Fatality rate represents number of bats killed per turbine per 7-month study period.

e

Fatality rate represents number of birds and bats killed per turbine per 6-week study period; however, 

bat mortality has been shown to be concentrated in the season during which these study periods took 

place.
Page 51 GAO-05-906 Wind Power

Appendix III

Comments from the Department of the 

Interior ApendxiI

Note: GAO comments 

supplementing those in 

the report text appear 

at the end of this 

appendix.

See comment 1.

See comment 2.
Appendix III

Comments from the Department of the 

Interior

Page 52 GAO-05-906 Wind Power

See comment 3.

See comment 4.
Appendix III

Comments from the Department of the 

Interior

Page 53 GAO-05-906 Wind Power
Appendix III

Comments from the Department of the 

Interior

Page 54 GAO-05-906 Wind Power

The following are GAO’s comments on the Department of the Interior’s 

letter dated September 2, 2005. 

GAO Comments The Department of the Interior raised one issue with our recommendation 

that we have addressed in the Agency Comment and Our Evaluation 

section in the report. We address below the four other points the 

department raised in its letter. In addition, the department provided 

technical comments that we have incorporated into the report, as 

appropriate.

1. We agree that it is important to point out that many of these studies 

were not scientifically peer-reviewed and have added a footnote to this 

effect in the body of the report. However, we disagree that in some 

cases protocols used in the studies were unknown. As we explain in 

appendix I, we only included studies that were determined to have 

reasonably sound methodologies. We did not include any study for 

which we were unable to assess the protocols or methodology. 

2. We believe the section on law enforcement reflects continued 

investigation of “take” of federal trust species by wind turbines and 

FWS’s and the Department of Justice’s enforcement and prosecutorial 

discretion, although we have added some clarification on these points.

3. We did not find any instances where state or local agencies that 

regulate wind power included in our review had incorporated or 

adopted the interim guidelines into their own jurisdictional 

requirements for approving wind power facilities. We did, however, find 

agencies in two states that had used the guidelines to inform either 

their development of regulations or their monitoring of the wildlife 

impacts at operating wind power facilities.

4. We did not assess how various local controls provide for protection of 

individual animals that are interjurisdictional in their life cycles. The 

section of the report that pertains to state wildlife laws is descriptive in 

nature and serves to highlight the fact that state laws sometimes 

provide additional protections to species, beyond federal laws, that 

may be affected by wind power. We added language to highlight that 

federal jurisdiction for migratory birds has not been delegated to the 

states, and that primary responsibility for the protection of these birds 

resides with the federal government (Interior).
Page 55 GAO-05-906 Wind Power

Appendix IV

GAO Contact and Staff Acknowledgments ApendxiIV

GAO Contact Robin Nazzaro (202) 512-3841

Staff 

Acknowledgments

In addition to the individual named above, Patricia McClure, Assistant 

Director; José Alfredo Gómez; Kimberly Siegal; and William Roach made 

key contributions to this report. Important contributions were also made 

by Judy Pagano, John Delicath, and Omari Norman.
Page 56 GAO-05-906 Wind Power

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