Fatalities at wind turbines may threaten population viability of a migratory bat

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DOI: 10.1016/j.biocon.2017.02.023
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Large numbers of migratory bats are killed every year at wind energy facilities. However, population-level impacts are unknown as we lack basic demographic information about these species. We investigated whether fatalities at wind turbines could impact population viability of migratory bats, focusing on the hoary bat (Lasiurus cinereus), the species most frequently killed by turbines in North America. Using expert elicitation and population projection models, we show that mortality from wind turbines may drastically reduce population size and increase the risk of extinction. For example, the hoary bat population could decline by as much as 90% in the next 50 years if the initial population size is near 2.5 million bats and annual population growth rate is similar to rates estimated for other bat species (λ = 1.01). Our results suggest that wind energy development may pose a substantial threat to migratory bats in North America. If viable populations are to be sustained, conservation measures to reduce mortality from turbine collisions likely need to be initiated soon. Our findings inform policy decisions regarding preventing or mitigating impacts of energy infrastructure development on wildlife.
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Fatalities at wind turbines may threaten population viability of a
migratory bat
W.F. Frick
, J.A. Szymanski
, T.J. Weller
S.C. Loeb
, R.A. Medellin
, L.P. McGuire
Bat Conservation International, PO Box 162603, Austin, TX 78716, USA
Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA
Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
American Wind Wildlife Institute, Washington, DC 20005-3544, USA
United States Fish and Wildlife Service, Endangered Species Program, U.S. Fish and Wildlife Resource Center, Onalaska, WI 54650, USA
United StatesDepartment of Agriculture Forest Service, Pacic Southwest ResearchStation, Arcata, CA 95521, USA
Department of Biology, Grand Valley State University, Allendale, MI 49401, USA
United States Department of Agriculture Forest Service, Southern Research Station, Clemson, SC 29634, USA
Instituto de Ecología, Universidad Nacional Autónoma de México, Distrito Federal 04510, Mexico
Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA
abstractarticle info
Article history:
Received 15 December 2016
Received in revised form 8 February 2017
Accepted 14 February 2017
Available online xxxx
Large numbers of migratory bats are killed every year at wind energy facilities. However, population-level
impacts are unknown as we lack basic demographic information about these species. We investigated whether
fatalities at wind turbines couldimpact populationviability of migratory bats, focusing on thehoary bat (Lasiurus
cinereus), the speciesmost frequently killedby turbines in North America. Usingexpert elicitationand population
projection models, we show that mortality from wind turbines may drastically reduce population size and
increase the risk of extinction. For example, the hoary bat population could decline by as much as 90% in the
next 50 years if the initial population size is near 2.5 million bats and annual population growth rate is similar
to rates estimated for other bat species (λ= 1.01). Our results suggest that wind energy development may
pose a substantial threat to migratory bats in North America. If viable populations are to be sustained,
conservation measures to reduce mortality from turbine collisions likely need to be initiated soon. Our ndings
inform policy decisions regarding preventing or mitigating impacts of energy infrastructure development on
© 2017 Elsevier Ltd. All rights reserved.
Expert elicitation
hoary bat
Lasiurus cinereus
population viability
wind energy
1. Introduction
Wind energy development is growing rapidly across the globe as a
renewable energy source. However, wind energy facilities are not with-
out environmental costs (Saidur et al., 2011). For example, large num-
bers of bats are killed at wind energy facilities (Arnett et al., 2016;
O'Shea et al., 2016). Over 300,000 bats are estimated to be killed annu-
ally at wind energy facilities in Germany (Lehnert et al., 2014; Voigt et
al., 2012) and over 500,000 are estimated to be killed annually across
Canada and the United States (Arnett and Baerwald, 2013; Hayes,
2013; Smallwood, 2013). Over the past decade, substantial numbers of
bat fatalities and increased growth in wind energy have raised concern
about the impacts of wind energy development on bat populations
(Kunz et al., 2007). A critical question for conservation planning is
whether these fatalities could drive populations to dangerously low
levels or even extinction.
Addressing this question is challenging because bats that migrate
latitudinally over long distances have the highest fatalities at wind ener-
gy facilities and areamong the least studied (Kunz et al., 2007). Basic de-
mographic parameters and even rough empirical estimates of
population size do not exist (Lentini et al., 2015). In general, reproduc-
tive rates for bats are low, which can impact their ability to respond to
mortality threats (Barclay and Harder, 2003). Lack of empirical demo-
graphic and population data for migratory bats, especially for non-colo-
nial species, limits the ability to quantitatively assess the potential
impact of wind energy on these species (Diffendorfer et al., 2015). The
challenges associated with empirical estimation will likely remain in-
surmountable into the foreseeable future given the ecology of these
Biological Conservation 209 (2017) 172177
Corresponding author at: Bat Conservation International, PO Box 162603, Austin, TX
78716, USA.
E-mail address: wfrick@batcon.org (W.F. Frick).
0006-3207/© 2017 Elsevier Ltd. All rights reserved.
Contents lists available at ScienceDirect
Biological Conservation
journal homepage: www.elsevier.com/locate/bioc
Determining the threat of wind energy development on migratory
bats highlights the common problem of how to assess threats to species
when critical data are lacking. Data from similar species or structured
elicitation of expert opinion can be used for conservation decision-mak-
ing when empirical data for a focal species are unavailable (Burgman et
al., 2011; Drescher et al., 2013; Martin et al., 2012). In recent decades,
expert elicitation has been used for a variety of conservation problems
(Donlan et al., 2010; Martin et al., 2005; Oberhauser et al., 2016;
Runge et al., 2011; Smith et al., 2007), and evaluations of the elicitation
method provide structured approaches to help guard against subjective
biases when eliciting expert opinion (Martin et al., 2012). Deciding
whether conservation measures are necessary to prevent or mitigate
impacts from wind energy development on populations of migratory
bats requires use of expert judgments and/or use of data from similar
taxa to quantify reasonable scenarios of population growth and
We use population projection models to explore whether fatalities
from wind turbines threaten the population viability of hoary bats
(Lasiurus cinereus), a wide-spread migratory species comprising the
highest proportion of bat fatalities (38%) at wind energy facilities in
North America (Arnett and Baerwald, 2013). Given the lack of empirical
data on key population parameters for hoary bats, we used data from
similar species as well as expert elicitation (Martin et al., 2012)toiden-
tify available data sources, provide estimates of unknown parameters,
and quantify uncertainty. Our objective was to assess the likelihood
that mortality from wind energy turbines poses a species-level threat
to hoary bats in North America to inform conservation decision-makers
about the potential impacts of energy infrastructure development on
migratory bats. We hypothesized that mortality from wind energy tur-
bines at installed capacity by 2014 was sufciently high to substantially
reduce theprobability of population stability and increase the probabil-
ity of extinction over the next 50 to 100 years.
2. Materials and methods
2.1. Expert elicitation
We used a structured elicitation method to obtain specicjudg-
ments or values from experts. Co-author JAS and colleagues served as
eliciting facilitators and identied the conservation problem (Does
mortality from wind turbines pose a threat to population viability of
hoary bats in North America?), selected the experts, and designed the
elicitation process. Nine experts (see Supporting Information) were
identied based on literature review and discussions with the bat ecol-
ogy and conservation community and invited to participate by JAS. Ex-
perts were chosen based on their research programs and publication
records relevant to migratory bat ecology with an intent to represent
a range of expertise (e.g. expertise in population dynamics, genetics,
physiology, life history, and conservation). The elicitation was conduct-
ed over an introductory webinar (September 22, 2014), in-person
meeting (October 2122, 2014), and a working webinar (December
22, 2014).
Experts were instructed on the expert elicitation process and in-
formed of the common pitfalls and biases that often impair expert judg-
ments (Martin et al., 2012), such as anchoring and overcondence
(Speirs-Bridge et al., 2010). Anchoring happens when an expert xes
on a benchmark value and cannot adjust away from the benchmark,
while overcondence occurs when an expert believes their judgement
is more accurate than is warranted (Martin et al., 2012). To help mini-
mize anchoring and over-condence, a four-step elicitation method
was used whereby experts provided a lower bound, upper bound, and
most likely estimate, and ranked their condence level that the true
value fell within the lower and upper bounds (Speirs-Bridge et al.,
2010). Experts were trained on the methodology by practicing seed
questions. Judgments were elicited using a modied Delphi method
(Burgman et al., 2011) whereby experts provided judgments
anonymously, responses were collated and discussed with the group,
and then experts were allowed to adjust their estimates anonymously
(Burgman et al., 2011; Martin et al., 2012). This structured approach
allowed for the benets of discussion among experts while guarding
against group think (Burgman et al., 2011). Experts completed multiple
rounds of elicitation until all experts were content with their responses
and indicated they were at least 80% condent that the true value fell
between their lowest and highest bounds.
Experts estimated the continental-wide population size of hoary
bats and four vital rates: adult annual survival, rst-year annual surviv-
al, adult fecundity, and rst-year fecundity (Tables S1, S2). Annual sur-
vival was estimated in the absence of mortality related to wind
energy. Bats typically cannot be aged after their rst autumn which
limits most demographic studies to two stages: young-of-the-year and
adult (Lentini et al., 2015; O'Shea et al., 2004) (Fig.S1). Empirical studies
on demography of other vespertilionid bats were used to inform expert
opinionson vital rates because no estimates exist for hoary bats,con-ge-
neric, or ecologically equivalent species (Lentini et al., 2015; O'Shea et
al., 2004). We calculated population growth rate (λ) as the dominant ei-
genvalue from a 2-stage Lefkovitch matrix (Caswell, 2001) using the
most likelyvital rate estimates from each expert using function
eigen.analysis in the popbio package of R (Stubben and Milligan, 2007).
2.2. Empirical estimates of bat population growth (λ)
We surveyed the literature for empirical estimates of bat population
growth rates based on calculation from vital rate matrices to compare
how values from expert elicitation compared to empirical studies of
other bat species. We searched the 27 papers used by Lentini et al.
(2015) that used vital rate estimation based on Cormack-Jolly-Seber
methods for published estimates of population growth and included
two additional recent studies that were published after Lentini et al.
(2015) to generate 14 published estimates of population growth rate
calculated from vital rate matrices for nine bat species (Table S3).
There is no indication of population structure for hoary bats in Canada
and the continental United States (Russell et al., 2015), so we assumed
a single open population and set immigration and emigration to zero.
2.3. Estimates of mortality from wind energy turbines in North America
Arnett and Baerwald (2013) estimated the number of bats killed by
wind turbines in Canada and theU.S. in 2012 (range: 196,190395,886),
of which 38% were hoary bats. We calculated fatalities per megawatt
(MW) based on installed capacity in North America in 2012
(66,213 MW) and adjusted fatality estimates (F
) to the installed ca-
pacity in 2014 (75,570 MW) (American WindEnergy Association, 2016;
Canadian Wind Energy Association, 2016). We kept installed capacity
constant at 2014 levels to reduce uncertainty in projecting future MW
capacity. We used the midpoint of the adjusted fatality estimate for
hoary bats (F
= 128.469) to calculate theproportion of the popula-
tion killed by wind turbines (F
), where N
is initial population
size, and applied that proportional mortality for each year in the simu-
lation. We assumed that an individual bat's probability of colliding
with a turbine would not depend on the density of bats, and therefore
used a constant mortality rate.
2.4. Population projection model
We projected stochastic population growth with and without mor-
tality from wind turbines across a range of mean population growth
rate (λ) values and initial population sizes (N
) to compare changes in
population stability after 50 years and probability of extinction after
100 years to identify the demographic scenarios for wh ich current levels
of mortality from wind turbines results in substantial population de-
clines or increased risk of extinction of hoary bats. We performed 100
projections (10,000 simulations per projection) using 10 sequential
173W.F. Frick et al. / Biological Conservation 209 (2017) 172177
values of mean population growth rate (λ) from 0.94 to 1.18 and 10 se-
quential values of initial population size (N
) from 1 to 10 million bats
based on ranges provided by expert elicitation and informed by empir-
ical studies of other bat species.
To account for annual variability in population growth, we used a
random draw generated from a log-normal distribution where μ=
=0.10(Morris and Doak, 2002)ateachtimestepin
each simulation. We used 0.10 for σ
to account for environmental var-
iation and uncertainty in λ(Morris and Doak, 2002). We xed a ceiling
on population growth at 10 times the initial population size to account
for carrying capacity and to balance between unbounded and overly
constrained population growth. We chose not to include additional
complexity of density-dependent population growth given the limita-
tions of available data for parameterization. We set a quasi-extinction
threshold at 2500 bats.
Population stability was calculated as the proportion of the remain-
ing population to the initial population after 50 years of projected
growth (N
). Probability of extinction was calculated as the fraction
of simulations where the population size fell below the quasi-extinction
threshold during 100 years of projected growth. We present the results
as isoline contours visualizing the combinations of N
and λvalues that
result in population stability or probability of extinction thresholds of
3. Results
Current rates of wind turbine fatalities are sufciently high to sub-
stantially change the probability of population stability and risk of ex-
tinction across a range of plausible demographic scenarios for hoary
bats (Figs. 1 and 2). Mortality from wind turbines increased the isoline
of stable population growth after 50 years indicating that annual popu-
lation growth rate (λ) would have to be substantially higher, particular-
ly at lower population sizes, to compensate for wind-associated
mortality (Fig. 1). The annual population growth rate would need to
be at least 6% per year (λ= 1.06) to maintain a stable population if ini-
tial population size was 2.5 million bats and as great as 14% per year if
there are only 1 million hoary bats (Fig. 1). Similarly, mortality from
wind turbines increased the isoline for population persistence,
indicating that mortality from wind turbines could also increase the
risk of extinction over the next 100 years (Fig. 2).
Mortality from windturbines could result in a 50% reduction in pop-
ulation size in just 50 years even in an optimistic scenario of a hoary bat
population as large as 10 million bats and a mean annual growth rate of
1% per year, which would otherwise support stable population growth
(Fig. 3). At the most likelydemographic scenario from the expert elic-
itation (N
= 2.5 million bats and pre-wind λ= 1.015), the median
projected population size after 50 years was reduced by 90% (Fig. 3)
and the probability of extinction increased to 22% (Fig. 4). Growth rate
Fig. 1. Comparison of the isolines of stable populationgrowth after 50 years of population
growth with(red) and without (blue)mortality from windenergy turbines for hoarybats.
Solid linesare the median values from 10,000 simulations and dottedlines show the 25th
and 75th quartiles. Population stability is positive above isolines and negative below the
isolines. Gray shaded area indicates where proportional mortality from wind turbines
changes population trajectories by shifting the isoline of population stability upward,
indicating that annual populat ion growth rates must be higher, especially at low
population sizes, to compensate for mortality associated with wind energy turbines for
populations to remain stable. (For interpretation of the references to colour in this gure
legend, the reader is referred to the web version of this article.)
Fig. 2. Comparison of the isolines showing population persistence (e.g. b1% of probability
of extinction) af ter 100 years of population gro wth with (red) and without (blue)
mortality from wind energy turbines for hoary bats. Population persistence is positive
above isolines a nd negative below the isolines. Gray shaded are a indicates where
proportional mortality from wind turbines changes population trajectories by shifting
the isoline upwa rd, indicating that annual population growt h rates must be higher,
especially at low popu lation sizes, to com pensate for mortality associated with wind
energy turbines for populations to persist. (For interpretation of the references to colour
in this gure legend, the reader is referred to the web version of this article.)
Fig. 3. Isoline contoursof projected population declines after50 years of simulatedgrowth
with proportional mortality ofhoary bats from wind energy turbines acrosscombinations
of possible initial population sizes (N
) and population growth rates (λ). Isolines display
the combinations of N
and λwhere the median population of 10,000 simulations after
50 years of simulated growth was stable (black line) or decreased by 25%, 50%, 75%, 90%
and 95%. The dotted line shows the isoline of population stability without wind
mortality for comparison as shown in Fig. 1.Opendiamondsshowthemost likely
values of N
and λfrom each of 8 experts from the expert elicitation. The orange lled
diamond indicates the median most likelyvalue for N
and λfrom expert elicitation.
(For interpretation of the references to color in this gure legend, the reader is referred
to the web version of this article.)
174 W.F. Frick et al. / Biological Conservation 209 (2017) 172177
and population size combinations from four experts fell above the iso-
lines for population stability and persistence, but values from the
other four experts fell well below the isolines of stability and persistence
(Figs. 3 and 4).
The median population growth rate (λ= 1.015) from the expert
elicitation was similar but slightly higher than the median of 14 pub-
lished estimates of population growth rate calculated from vital rate
matrices for other bats species (λ= 1.0025) (Fig. 5).
4. Discussion
Reports of large numbers of bats killed at wind energy facilities have
attracted conservation attention for the past decade (Kunz et al., 2007).
However, the lack of basic demographic information about bats in gen-
eral and migratory bats specically, has hindered our ability to empiri-
cally address whether bat fatalities from wind energy developments
presents a serious threat to the viability of these species (Diffendorfer
et al., 2015). Likewise, few studies have directly estimated population-
level impacts from mortality from wind turbines on bird populations
(Carrete et al., 2009; Schaub, 2012; Stewart et al., 2007), although nu-
merous studies have documented collision rates for both birds and
bats (see Arnett et al., 2016; Erickson et al., 2014 for recent reviews).
We parameterized population models using a range of values from ex-
pert elicitation and informed from empirical estimates from other bat
species and show that, across a range of plausible demographic scenar-
ios, current mortality from wind turbines could result in rapid and se-
vere declines of bat populations within 50 years and increased risk of
extinction in 100 years.
For hoary bat populations to sustain stable, persisting popula-
tions with levels of mortality from wind turbines current through
2014 in North America, the mean annual population growth rate
must be substantially higher than what appears most likely from
both the expert elicitation exercise and empirical estimates from
other bat species. While two experts provided demographic esti-
mates that produced robust population growth rates (λ=1.16
and λ= 1.18; i.e., growth rates of 1618% more bats per year)
and a few empirical estimates were similarly high (Fig. 5), the me-
dian values of λfrom published studies and expert opinion (λ=
1.0025 and λ= 1.015, respectively) suggest much more modest
population growth rates that were sufcient for stable populations
in the absence of wind energy associated mortality but that are too
low to sustain the level of observed mortality currently caused by
wind turbines. As expected, the impact of wind energy related
mortality is most dramatic and concerning at lower population
sizes, although we note that even at the optimistic scenario of at
least 10 million bats, the isolines for both population stability and
persistence were shifted upwards, indicating that increased popu-
lation growth is necessary to compensate for wind-associated mor-
tality even at large population sizes. In contrast to the availability
of empirical estimates for population growth from other bat spe-
cies, there is scant information available about the total population
sizes of bats. Six of the eight experts put their most likely estimate
at or below 2.5 million bats. If the hoary bat population is around
2.5 million bats, our results suggest that growth rates that we ex-
pect as reasonable for bat populations (λ= 1.01) would result in
a 90% decline of the population in 50 years.
Although our modeling focused on hoary bats, the qualitative con-
clusions are likely broadly informative about the relative risk to other
migratory species that share similar life histories and high fatality
rates at wind turbines, such as eastern red bats (Lasiurus borealis) and
silver-haired bats (Lasionycteris noctivagans) in North America (Arnett
and Baerwald, 2013) and noctule bats (Nyctalus noctula) in Europe
(Lehnert et al., 2014). Future work combining expert elicitation and
modelingcould examine vulnerability to other specieswith high fatality
rates to identify species most at risk. In North America, species that mi-
grate latitudinally and do not hibernate for extended periods in caves
and mines do not appear at high risk from white-nose syndrome, a dis-
ease that causes high mortality for hibernating bats (Frick et al., 2010,
2015; Langwig et al., 2015). Fortunately, fatality rates from wind tur-
bines are typically lower for many of the species susceptible to white-
nose syndrome (Arnett and Baerwald, 2013; Langwig et al., 2012), yet
the combined effects of mortality from disease and wind turbines may
threaten some species (Erickson et al., 2016).
The range of scenarios we modeled was based on current available
information and conservative estimates of bat fatalities. We used the
lowest published estimate of bat fatality rate although higher estimates
of annual fatality rates have also been published (Hayes, 2013;
Smallwood, 2013). Furthermore, we held megawatt capacity constant
at installed capacity in 2014 and did not account for future growth of
Fig. 4. Isolinecontours of probability of extinction after 100 yearsof simulated population
growth with proportional mortality from wind energy turbines across combinations of
possible initia l population siz es (N
) and population growth rates (λ)forhoarybats.
Isolines display the combinations of N
and λwhere the proportion of populations (b1%,
25%, 50%, 75%, 99%) of 10,000 simulations went extinct during 100 years of simulated
population grow th. The dotted line shows the isoline of persistence (b1% chance of
extinction) without wind mortality for comparison as shown in Fig. 2. Open diamonds
show the most likelyvalues of N
and λfrom each of 8 experts from the expert
elicitation. The orange lled diamond indicates the median most likelyvalue for N
λfrom expert elicitation. (For interpretation of the references to color in this gure
legend, the reader is referred to the web version of this article.)
Fig. 5. Histograms of 10,000 simulated λvalues drawnfrom a log normal distribution. The
black histogram centers on the median of 14 reported values of λfrom empirical studies
on bat species. The orange histogram centers on the median λfrom expert elicitation.
All simulations used a variance at 0.10 to account for environmental variation and
uncertainty in population growth. Rug values show reported λ's from published studies
(black) and expert elicitation (orange). (For interpretation of the references to color in
this gure legend, the reader is referred to the web version of this article.)
175W.F. Frick et al. / Biological Conservation 209 (2017) 172177
the wind energy industry to reduce other forms of uncertainty in the
models. Wind energy currently represents approximately 5% of electric-
ity generation in Canada and U.S.A., with a target of increasingto 20% by
2025 in Canada and by 2030 in U.S.A (American Wind Energy
Association, 2016; Canadian Wind Energy Association, 2016). Installed
capacity increased by over 5100 MW (a 7% increase from 2014 installed
capacity) in 2015 alone (American Wind Energy Association, 2016;
Canadian Wind Energy Association, 2016). With more turbines and no
reductions in fatality rates at wind energy facilities, we expect fatalities
and species-level impacts to migratory bats to increase (i.e., greater de-
clines in N). Future modeling efforts should explore the impact of in-
creased turbine development and assessment of how mitigation
efforts can be applied to reduce population-level impacts.
The only method documented to reduce fatalities at wind turbines is
limiting operation during high risk periods, such as nocturnal periods of
low wind speeds during autumn migration (Arnett et al., 2011;
Baerwald et al., 2009). Such operational curtailment can reduce bat fa-
talities by 4493% with minimal impact on power generation (Arnett
et al., 2011). The American Wind Energy Association recently adopted
policies to limit blade movement in low wind speeds as a voluntary op-
erating protocol to reduce fatalities (American Wind Energy
Association, 2015). Industry-wide implementation of operational miti-
gation or emerging technologies (e.g. acoustic deterrents; Arnett et al.,
2013) may be necessary to successfully manage migratory bat
populations and ensure stable and viable populations in North America.
Siting wind energy facilities in places perceived as lower risk for causing
bat fatalities could also help reduce impacts, although further research
is needed to determine the efcacy of predicting risk from pre-siting
assessments (Baerwald and Barclay, 2009; Hein et al., 2013; Lintott
et al., 2016).
Conservation decisions must often be made with imperfect knowl-
edge and data gaps. We lack empirical data on population sizes and
trends for hoary bats and other migratory bat species, and given the
ecology of these species and technologies available, we are unlikely to
collect empirical population data in the near future. Our analyses sug-
gest there is a range of realistic possibilities for the impact of fatalities
from wind turbines that includes substantial population declines and
increased risk of extinction. The magnitude of these predicted impacts
may warrant re-evaluation of thestatus of hoary batsfrom least concern
to a threatened category on the IUCN Red List (IUCN, 2012). Given the
possibility for near or total extinction from wind-energy-related fatali-
ties, our results suggest that conservation planning to manage migrato-
ry bat populations should include actionsto reduce bat fatalities at wind
energy facilities in North America.
We thank Todd Katzner and two anonymous reviewers for com-
ments on the manuscript. Robyn Niver, Lori Pruitt, and Dan Nol
helped with designing and conducting the elicitation workshop
andprovidedcommentsonearlierdrafts. David Nelson and Ste-
phen Keller provided information to experts during the introducto-
ry phase of the elicitation workshop. Taal Levi, Ed Arnett, Paul
Cryan, and Maarten Vonhof contributed to earlier versions of the
modeling effort. The ndings and conclusions in this article are
those of the authors and do not necessarily represent the views of
the U.S. Fish and Wildlife Service. USFWS, Region 3, provided travel
to the elicitation workshop. WFF was supported on NSF DEB-
1115895/1336390. RMRB is supported by Natural Sciences and En-
gineering Research Council of Canada.
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  • Technical Report
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    The U.S. Geological Survey has developed a methodology to assess the impacts of wind energy development on wildlife; it is a probabilistic, quantitative assessment methodology that can communicate to decision makers and the public the magnitude of these effects on species populations. The methodology is currently applicable to birds and bats, focuses primarily on the effects of collisions, and can be applied to any species that breeds in, migrates through, or otherwise uses any part of the United States. The methodology is intended to assess species at the national scale and is fundamentally different from existing methods focusing on impacts at individual facilities. Publicly available fatality information, population estimates, species range maps, turbine location data, biological characteristics, and generic population models are used to generate both a ranked list of species based on relative risk as well as quantitative measures of the magnitude of the effect on species’ population trend and size. Three metrics are combined to determine direct and indirect relative risk to populations. A generic population model is used to estimate the expected change in population trend and includes additive mortality from collisions with wind turbines. Lastly, the methodology uses observed fatalities and an estimate of potential biological removal to assess the risk of a decline in population size. Data for six bird species have been processed through the entire methodology as a test case, and the results are presented in this report. Components of the methodology are based on simplifying assumptions and require information that, for many species, may be sparse or unreliable. These assumptions are presented in the report and should be carefully considered when using output from the methodology. In addition, this methodology can be used to recommend species for more intensive demographic modeling or highlight those species that may not require any additional protection because effects of wind energy development on their populations are projected to be small.
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