Bat Acoustical Surveys at the 

National Renewable Energy 

Laboratory, National Wind 

Technology Center 

July 2010 – November 2010 

Carron Meaney and Jenny Gerson

Walsh Environmental Scientists and Engineers, LLC

Boulder, Colorado

NREL Technical Monitor: Tom Ryon

NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Subcontract Report

NREL/SR-1900-70461 

July 2018

Contract No. DE-AC36-08GO28308
National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

Bat Acoustical Surveys at the 

National Renewable Energy 

Laboratory, National Wind 

Technology Center 

July 2010 – November 2010 

Carron Meaney and Jenny Gerson

Walsh Environmental Scientists and Engineers, LLC

Boulder, Colorado

NREL Technical Monitor: Tom Ryon 

Prepared under Subcontract No. LGF-0-40734-01 

Suggested Citation

Meaney, Carron; Gerson, Jenny. 2018. Bat Acoustical Surveys at the National

Renewable Energy Laboratory, National Wind Technology Center: July- November

2010. Golden, CO: National Renewable Energy Laboratory. NREL/SR-1900-70461. 

https://www.nrel.gov/docs/fy18osti/70461.pdf. 

NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Subcontract Report

NREL/SR-1900-70461 

July 2018

Contract No. DE-AC36-08GO28308
This publication was reproduced from the best available copy

submitted by the subcontractor and received no editorial review at NREL.

NOTICE

This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable 

Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding 

provided by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy. The views 

expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. This report is 

available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. 

U.S. Department of Energy (DOE) reports produced after 1991 

and a growing number of pre-1991 documents are available 

free via www.OSTI.gov. 

Cover Photos by Dennis Schroeder: (left to right) NREL 26173, NREL 18302, NREL 19758, NREL 29642, NREL 19795.

NREL prints on paper that contains recycled content. 
Bat Acoustical Surveys at the 

National Renewable Energy Laboratory, 

National Wind Technology Center 

Jefferson County, Colorado 

May 5, 2011 

Prepared for 

Prepared by 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

i 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY .............................................................................................. 1

INTRODUCTION............................................................................................................. 2

METHODS ........................................................................................................................ 2

Field Work ................................................................................................................................ 2

Data Management and Analysis ............................................................................................... 4

RESULTS .......................................................................................................................... 5

Detector Nights ......................................................................................................................... 5

Bat Passes and Species Composition ........................................................................................ 5

Activity Index ........................................................................................................................... 6

Temporal Distribution ............................................................................................................... 6

Peak Activity Levels ................................................................................................................. 8

Special Status Species ............................................................................................................... 8

DISCUSSION .................................................................................................................... 8

Detector Nights ......................................................................................................................... 8

Bat Passes and Species Composition ........................................................................................ 8

Activity Index ........................................................................................................................... 9

Temporal Distribution ............................................................................................................... 9

Peak Activity levels ................................................................................................................ 10

Special Status Species ............................................................................................................. 10

RECOMMENDATIONS ................................................................................................ 10

REFERENCES ................................................................................................................ 10
Bat Survey Report 

NWTC, Jefferson County, Colorado 

ii 

TABLES 

Table 1. Detector Nights, NWTC, Jefferson County, Colorado 2010. ............................................ 5

Table 2. Identified Bat Passes and Index of Activity, NWTC, Jefferson County, Colorado 2010. 6

Table 3. Temporal Distribution of Bat Activity, NWTC, Jefferson County, Colorado 2010. ........ 7

Table 4. Baseline Bat Activity at NWTC Compared with Wind Energy Facilities. ....................... 9

FIGURES 

Figure 1. AnaBat Detector Location, NWTC, Jefferson County, Colorado, 2010 .......................... 3

Figure 2. Bat Species Composition by Identified Bat Passes, NWTC, Jefferson County, Colorado 

2010. ................................................................................................................................ 5

Figure 3. Index of Bat Activity by Month, NWTC, Jefferson County, Colorado 2010. ................. 7

Figure 4. Peak Activity Levels, by Total Bat Passes, NWTC, Jefferson County, Colorado, 2010 . 8

 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

iii 

LIST OF ACRONYMS 

CDOW Colorado Division of Wildlife 

CF compact flash 

NWTC NREL’s National Wind Technology Center 

Mic microphone 

Walsh Walsh Environmental Scientists and Engineers 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

1 

EXECUTIVE SUMMARY 

An acoustical bat use survey was conducted at the NWTC from July 6, 2010 to November 7, 

2010, using a passive acoustical method with AnaBat Systems Bat Detectors (Titley Electronics). 

The purpose of this survey was to obtain information about use by bats within the Project area. 

All data were collected from one bat detector was mounted on a fence post within the 

conservation easement in the northwest portion of the site. Bat activity was determined by the 

number of bat passes (number of echolocation calls recorded with ≥ 2 chirps) per detector night. 

Species composition, temporal distribution (by month), and peak activity levels were analyzed. 

A total of 12,425 bat passes was recorded during the survey period for an index of activity of 

99.40 bat passes per detector night. Of the 12,425 total bat passes, 8,772 passes could be 

identified to species (70.18 identified bat passes per detector night). 

Species identified included big brown bat, eastern red bat, fringed myotis, hoary bat, silver-haired 

bat, and Myotis bat group (which may include western small-footed myotis, western long-eared 

myotis, little brown myotis, and long-legged myotis). 

Most bats were detected in July (3,952 total bat passes) and August (5,058 total bat passes). The 

Myotis bat group was most the most frequently detected (4,373 identified bat passes). 

There were no peaks of activity during the monitoring period, but rather constant fluctuation. 

No Federally- or state-listed threatened, endangered, or candidate species or species of special 

concern were identified during surveys (USFWS 2010, CDOW 2010). 

 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

2 

INTRODUCTION 

Walsh Environmental Scientists and Engineers, LLC (Walsh) was retained by the National 

Renewable Energy Laboratory (NREL) to conduct acoustic bat surveys at the National Wind 

Technology Center (NWTC). This effort involved using passive acoustical detectors that recorded 

bat echolocation calls from July to November 2010. This report presents the results of these 

surveys. 

NWTC is located on approximately 320 acres in Jefferson County, Colorado, on State Highway 

128 between the cities of Boulder and Golden, Colorado adjacent to the eastern foothills of the 

Rocky Mountains. The legal description of the current boundary is: T2N, R70W, portions of 

Sections 3 and 4. 

The site is largely composed of Xeric mixed grassland. The bat monitoring unit was located in a 

draw within a conservation easement in the western portion of the site. There is a small stand of 

ponderosa pines directly east of the unit, a small ephemeral pond a few hundred yards south, and 

a larger, long-lasting pond one-half mile south (Figure 1). 

METHODS 

Field Work 

Bat echolocation calls were recorded from July 6 to November 7, 2010, using an AnaBat SD2 

ultrasonic detector from Titley Electronics, Ballina, Australia. One AnaBat detector was installed 

on a fencepost within the conservation easement at roughly 0.5 meters above the ground. It is 

recognized that attenuation of bat calls occurs at roughly 30 meters from the unit, indicating that 

the detector was able to capture calls about 30 meters above the ground. 

Data collection methods followed Kunz et al. (2007). Call recording was conducted during 

crepuscular and nocturnal hours (about one hour before sunset to one hour after sunrise) to 

capture peak times of bat activity (Reynolds 2006). All files recorded during the survey period 

were saved to 1 gigabyte compact flash (CF) cards that were collected at two- to three-week 

intervals and downloaded to a computer using Titley’s CF card reader software. 

 
!5

Coal C re ek

S p ri n g B r o o k

Lafarge

Pond

105°14'3.6"W, 39°54'50.64"N

20110304U:\Pr ojects\900758.0001.010_nr el_nwtc \m ap_m xd\anabat_location.mx d

Figure 1. AnaBat Detector Location

NREL National Wind Technology Center

Jefferson County, CO

May 3, 2011 | 900758.0001.020

!5 Anabat Location

NWTC Boundary

Ponderosa Pine Woodland

Conservation Area

National Hydrography Dataset

Artificial Path

Canal Ditch

Pipeline

Intermittent Stream/River

Perennial Stream/River

0 0.25 0.5 1

Miles

1:18,000

1 in = 1,500 feet $
Bat Survey Report 

NWTC, Jefferson County, Colorado 

4 

Data Management and Analysis 

Data gathered from the AnaBat detector were analyzed using Analook software. A preliminary 

analysis was run to separate extraneous noise files (which may include noise created by weather, 

radio or microwaves, insects, birds, etc.) from bat echolocation call files. The number of bat calls 

could then be determined and reported using the metric “bat pass.” A bat pass is an accepted 

measure of bat activity defined as an echolocation sequence of at least two echolocations pulses, 

or chirps, with a minimum pulse duration of 10 milliseconds within each sequence, separated by 

more than one second (Gannon et al. 2003, Kunz et al. 2007). Bat call files were further identified 

and segregated into species groups to show species composition of bats on the site. A number of 

calculated variables are derived from the bat pass data and are described below. 

Bat passes were identified to species or species group when possible, and this subset of bat passes 

is termed “identified bat pass.” Identified bat passes included all bat passes that had five or more 

clear echolocation calls, or chirps. Myotis bats are a group whose individual species’ calls are 

difficult to distinguish. These calls are therefore lumped as Myotis bats, and may include one or 

more of the following species known to occur along the Front Range of Colorado: western smallfooted myotis (Myotis ciliolabrum), western long-eared myotis (Myotis evotis), little brown 

myotis (Myotis lucifugus), and long-legged myotis (Myotis volans). The fringed myotis (Myotis 

thysanodes) is an exception as its calls are distinct. 

An index of relative bat activity, or activity index, was calculated as the number of bat passes per 

detector night (the number of nights the detector was recording data). Additionally, an activity 

index was determined per species by using the number of identified bat passes for each species 

per detector night. Other metrics calculated from the data include temporal distribution of bat 

activity by month and peak activity. 

Two important assumptions are required for these data analyses that may not be completely 

supported: 

1) Each bat pass accounts for a single bat recorded only once by the AnaBat detector. 

One bat pass may actually contain more than one individual bat echolocating, or 

alternatively, multiple bat passes may be the same bat circling around and echolocating. 

However, recognition of individuals cannot be determined using AnaBat detectors, so the 

analysis must be conducted with one bat pass equivalent to one bat. 

2) All species are equally well detected by AnaBat detectors. Different species of bats 

echolocation calls attenuate at differing distances, with some species of bats whose calls 

attenuate at shorter distances being recorded less often than those whose calls carry 

further. For example, Townsend’s big-eared bat (Corynorhinus townsendii) has a weak 

call that attenuates quickly and is not as readily detected as many other species (Piaggio 

2005). Furthermore, behavioral differences may result in certain species being recorded 

more often than others. Since there is no appropriate way to correct for these differences, 

detection equality must be assumed (Gannon et al. 2003). 

During data analysis, any special status species, i.e., Federally- or state-listed threatened, 

endangered, or candidate species, or species of special concern were noted (USFWS 2010, 

CDOW 2010). 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

5 

RESULTS 

Detector Nights 

One AnaBat detector recorded data for 125 detector nights, every night from July 6 to November 

7, 2010 (Table 1). 

Table 1. Detector Nights, NWTC, 

Jefferson County, Colorado 2010. 

Month Detector Nights

July 26

August 31

September 30

October 31

November 7

Total 125

Bat Passes and Species Composition 

A total of 12,425 bat passes were recorded during the survey period. Of those, 8,772 were 

identified to species. Species composition is summarized in Figure 2 and included 50 percent 

Myotis bats (Myotis sp.) (4,373 identified bat passes), 36 percent big brown bat (Eptesicus 

fuscus) (3,145 passes), 7 percent fringed myotis (592 passes) (Myotis thysanodes), 5 percent 

silver-haired bat (Lasionycteris noctivagans) (481 passes), 2 percent hoary bat (Lasiurus 

cinereus) (179 passes), and less than 1 percent eastern red bat (Lasiurus borealis) (2 passes). 

Figure 2. Bat Species Composition by Identified Bat Passes, NWTC, 

Jefferson County, Colorado 2010. 

 

Big brown

bat

Eastern red

bat

Hoary bat

Silver‐haired

bat

Myotis bats

Fringed

myotis
Bat Survey Report 

NWTC, Jefferson County, Colorado 

6 

Activity Index 

There are two indices of bat activity: total bat passes, which includes all echolocation calls with 

two or more chirps, and identified bat passes, which is limited to those with five or more chirps 

(see Methods). The overall activity index recorded at the AnaBat detector was 99.40 total bat 

passes per detector night and 70.18 identified bat passes per detector night (Table 1). The species 

of bat with the highest activity index is the Myotis bat group (34.98 bat passes per detector night). 

Big brown bat also had comparatively high levels of activity (25.15 bat passes per detector night). 

Fringed myotis, silver-haired bat, and hoary bat had comparatively moderate levels of activity, 

between 1.43 to 4.74 identified bat passes per detector night. Eastern red bat had a comparatively 

low level of activity (0.02 identified bat passes per detector night) (Table 2). 

Table 2. Identified Bat Passes and Index of Activity, NWTC, Jefferson County, 

Colorado 2010. 

Common Name Scientific Name Number

Identified  

Index of Activity (Number

Identified/Detector Nights)

Myotis bats* Myotis sp. 4,373 34.98 

Big brown bat Eptesicus fuscus 3,145 25.15 

Fringed myotis Myotis thysanodes 592 4.74 

Silver-haired bat Lasionycteris 

noctivagans 481 3.85 

Hoary bat Lasiurus cinereus 179 1.43 

Eastern red bat Lasiurus borealis 2 0.02 

Total Identified Bat Passes 8,772 70.18 

Total Bat Passes 12,425 99.40 

*Included in this group may be one or more of the following species: western small-footed myotis, western long-eared myotis, little 

brown myotis, and long-legged myotis. 

Temporal Distribution 

Total bat activity was highest in July (3,952 bat passes) and August (5,058 bat passes) with an 

activity index of 152.04 and 163.16 total bat passes per detector night, respectively. September 

was also a month of high bat activity (3,221 bat passes) with an activity indices of 107.37 total 

bat passes per detector night. October and November had relatively low levels of bat activity (190 

and 3 bat passes) with activity indices of 6.13 and 0.43 total bat passes per detector night, 

respectively (Figure 3, Table 3). 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

7 

Figure 3. Index of Bat Activity by Month, NWTC, Jefferson County, 

Colorado 2010. 

 

(0.43 bat

passes/detector

night)

0

20

40

60

80

100

120

140

160

180

July August September October November

Index of Bat Activity

 Note: Index of bat activity is determined by number of bat passes per detector night for that month; detector nights are shown 

 in Table 1. 

Identified bat passes were also highest in July (3162) and August (3,299 bat passes) with an 

activity index of 121.62 and 106.42 identified bat passes per detector night, respectively. Bat 

activity was moderate in September, lower in October, and very low in November. 

Big brown bats, Myotis bats, and hoary bats experienced their highest activity in July and August 

(Table 3), with hoary bats active at much lower frequencies than the other two species/groups. 

Fringed myotis were active in July, August and September; silver-haired bats were most active in 

September but maintained a presence in July and August as well. Eastern red bats had very low 

activity, though were present in July and August. 

Table 3. Temporal Distribution of Bat Activity, NWTC, Jefferson County, 

Colorado 2010. 

Species July Aug Sept Oct Nov 

Big brown bat 58.15 39.97 12.37 0.68 0.14 

Eastern red bat 0.04 0.03 0.00 0.00 0.00 

Fringed myotis 6.38 6.74 7.13 0.10 0.00 

Hoary bat 2.53 3.03 0.63 0.00 0.00 

Myotis bats 51.19 52.06 46.13 1.42 0.00 

Silver-haired bat 3.31 4.55 6.37 1.97 0.29 

Total Identified Bat 

Passes 121.62 106.41 72.63 4.16 0.43 

Total Bat Passes 152.04 163.16 107.16 6.13 0.43 

Note: Bat activity determined by number of identified bat passes per detector night for that month. 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

8 

Peak Activity Levels 

The level of bat activity fluctuates consistently from the beginning of monitoring in July through 

the end of September, when levels drop off (Figure 4). Although there are no true peaks of 

activity, which would be indicated by a fairly steady rise to a high point in activity, there are 

several spikes in activity that can be seen on July 21 (315 bat passes), August 18 (390 bat passes), 

August 26 (370 bat passes), August 28 (309 bat passes) and September16 (322 bat passes). 

Figure 4. Peak Activity Levels, by Total Bat Passes, NWTC, Jefferson 

County, Colorado, 2010 

0

100

200

300

400

500

Special Status Species 

No Federally-listed threatened, endangered or candidate bat species listed by the Endangered 

Species Act are known to occur in Colorado (USFWS 2010). No state-listed threatened or 

endangered species or species of special concern were identified during surveys (CDOW 2010). 

DISCUSSION 

Detector Nights 

The AnaBat detector ran every night without obvious problems from July 6, 2010 to November 7, 

2010. 

Bat Passes and Species Composition 

The Myotis bat group was the most commonly detected group during monitoring with 4,373 

identified bat passes, or nearly half of all identified bats. Since it is very difficult to differentiate 

echolocation calls of the species in this group, they were not identified to species. The species of 

Myotis that are known to inhabit this region include western small-footed myotis, western longeared myotis, little brown myotis, and long-legged myotis. The Myotis group may be made up of 

any of these species. Since this group was detected throughout July, August, and September, they 

are most likely resident bats. Big brown bats were the second most commonly detected group 

with 3,144 identified bat passes. Their presence throughout July, August, and September also 

shows that they are most likely resident bats. 

Of the 18 species of bats documented in Colorado (Armstrong et al. 1994; Fitzgerald et al. 1994), 

a minimum of 6 species and up to 9 species were identified on site (depending on how many 

Myotis species are present in the Myotis bat group). Several calls recorded may have been pallid 

bat calls (Antrozous pallidus), but due to the unlikely event that this species would occur along 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

9 

the foothills, and that aspects of pallid bat calls look very similar to either big brown bats or little 

brown myotis, these calls were not identified as pallid bats. Although Colorado bat populations 

and distribution have not been thoroughly studied, these results are consistent with what is 

generally known about the bat populations within the state (Adams 2003, Armstrong et al. 1994). 

Activity Index 

Total bat passes for the survey period was 99.40 per detector night. Although data may not be 

perfectly comparable with monitoring done at wind farms, this level of activity is much higher 

than what has been found for projects in this and other regions of the U.S (Table 4). It is not 

known why the levels of activity on this site are so high. Several hypotheses include: 

1) The Ponderosa pines, shrubs, and grasses in the draw where the AnaBat unit was 

located provide good foraging for bats, as well as potential roosting sites in the trees; 

2) The large pond on the Lafarge mining property (Spicer) 0.5 mile to the south of the 

AnaBat unit is the best quality and closest water source to bat roosts, and this water 

source is available through the summer, when smaller water sources will become dry; 

3) The rocky ridgeline of the foothills, roughly two miles to the west, provides good 

roosting habitat, a limiting factor for bats; and 

4) Vacant buildings on Lafarge’s property may provide good roosting habitat for big and 

little brown bats. 

Table 4. Baseline Bat Activity at NWTC Compared with Wind Energy 

Facilities.

Wind Energy Facility 

Bat Activity 

(total bat passes/detector 

night) 

Reference 

Colorado Highlands, CO 0.23 Walsh 2010 

Top of the World, WY 0.58 Rintz and Kimberly 2009 

Dunlap Ranch, WY 1.67 Johnson et al. 2009 

Campbell Hill, WY 2.03 Taylor et al. 2008 

Buffalo Mountain, TN 23.70 Fiedler 2004 

Mountaineer, WV 38.30 Arnett et al. 2005 

NWTC, CO 99.40 This report 

Temporal Distribution 

For all species combined, the highest number of bat passes was recorded in July and August. This 

suggests that the majority of recorded bat passes are from local, resident bats. Bat passes recorded 

in late August, September, and October may be related to fall migration. This coincides with 

other studies that have found high levels of bat activity in the late summer and early fall

(Erickson et al. 2002, Cryan 2003, Kunz et al. 2007). 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

10 

Big brown bats appear to be resident, as they are most active in July and August. Myotis bats, 

active July through September on site, may delay migration until later in September. Fringed 

myotis is also likely resident, with activity from July through September and their known 

presence in the general vicinity (Rick Adams, personal communication, March 11, 2011). Silverhaired bats show some resident activity with a presence in July and August; the higher activity in 

September is indicative of their migratory behavior. Hoary bats are solitary and seldom abundant, 

suitably reflected in their low abundance in July and August. The eastern red bat was present in 

July and August but very infrequently and is uncommon in Colorado. 

Peak Activity levels 

Bat activity fluctuated from July to September and then decreased until the end of the monitoring 

period with no true peaks of activity. This, again, suggests that most of the bat activity captured 

during the summer was of resident bats. The fluctuation of activity levels, as well as the spikes of 

activity, may be due to weather or other factors that influence the activity of bats. 

Special Status Species 

No special status species were identified during acoustical bat surveys. Townsend’s big-eared bat, 

the only state-listed bat species, is known to occur near this area (Adams 2003). Maternity 

colonies have been identified and are protected at Harmon and Mallory caves on City of Boulder 

Open Space and Mountain Parks land roughly 5 miles to the north/northwest 

(http://www.bouldercolorado.gov/files/openspace/closure_documents/MalloryHarmonCave_Whit

eNoseSyndrome.pdf). 

RECOMMENDATIONS

Walsh recommends several additional surveys which will help to better understand bat movement 

and activity at NWTC. 

• Continued passive acoustical monitoring of bats from April 1 to July 6 to complete a full 

year of monitoring. 

• Continued monitoring in subsequent years to substantiate patterns seen in this study as 

well as provide year-to-year comparisons. 

• Additional passive acoustical monitoring at different locations and heights to see the 

movement of bats through the site 

• Mist netting surveys can better identify which species are using the site 

• Putting radio-tags on some bats can show where they are roosting. 

REFERENCES 

Adams, R.A. 2003. Bats of the Rocky Mountain West: natural history, ecology, and conservation. 

University Press of Colorado, Boulder. 

Armstrong, D.M., R.A. Adams, K.W. Navo, J. Freeman, and S.J. Bissell. 1994. Bats of Colorado: 

Shadows of the Night. Colorado Division of Wildlife, Denver, Colorado. 
Bat Survey Report 

NWTC, Jefferson County, Colorado 

11 

Arnett, E.B., W.P. Erickson, J. Kerns, and J. Horn. 2005. Relationships between Bats and Wind 

Turbines in Pennsylvania and West Virginia: An Assessment of Fatality Search 

Protocols, Patterns of Fatality, and Behavioral Interactions with Wind Turbines. Prepared 

for the Bats and Wind Energy Cooperative. 

Colorado Division of Wildlife (CDOW). 2010. Colorado Endangered, Threatened and Species of 

Special Concern. 

http://wildlife.state.co.us/WildlifeSpecies/SpeciesOfConcern/Mammals/MammalsOfCon

cern.htm 

Cryan, P.M. 2003. Seasonal distribution of migratory tree bats (Lasiurus and Lasionycteris) in 

North America. Journal of Mammalogy. 84(2):579-593. 

Erickson, W., G. Johnson, D. Young, D. Strickland, R. Good, M. Bourassa, K. Bay, and K. 

Sernka. (2002). Synthesis and comparison of baseline avian and bat use, raptor nesting 

and mortality information from proposed and existing wind developments. Western 

EcoSystems Technology, Inc. Prepared for Bonneville Power Administration. 

Fiedler, J.K. 2004. Assessment of bat mortality and activity at Buffalo Mountain Windfarm, 

eastern Tennessee. M.S. Thesis, University of Tennessee, Knoxville. 

Fitzgerald, J.P., C.A. Meaney, and D.M. Armstrong. 1994. Mammals of Colorado. University 

Press of Colorado, Niwot, and Denver Museum of Natural History, Denver. 

Gannon, W.L., R.E. Sherwin, and S. Haymond. 2003. On the importance of articulating 

assumptions when conducting acoustic studies of bats. Wildlife Society Bulletin. 31:45-

61. 

Johnson, D., K. Bay, J. Eddy. 2009. Final Report: Wildlife Baseline Studies for the Dunlap Ranch 

Wind Resource Area, Carbon County, Wyoming. Western EcoSystems Technology, Inc. 

Prepared for CH2MHill. 

Kunz, T.H., E.B. Arnett, B.A. Cooper, W.P Erickson, R.P. Larkin, T.J. Mabee, M.L Morrison, 

M.D. Strickland, and J.M. Szewczak. 2007. Assessing impacts of wind-energy

development on nocturnally active birds and bats. A guidance document. Journal of

Wildlife Management. 71(8):2449-2486

Piaggio, A (Original account by Sherwin, R. 1998) 2005. Species Accounts: Townsend’s bigeared bat. Western Bat Working Group. 

http://www.wbwg.org/speciesinfo/species_accounts/vespertilonidae/coto.pdf 

Reynolds, D.S. 2006. Monitoring the potential impact of a wind development site on bats in the 

Northeast. Journal of Wildlife Management. 70:1219-1227. 

Rintz, T. and Bay, K. 2009. Final Report: Wildlife Baseline Studies for the Top of the World 

Wind Resource Area, Converse County, Wyoming. Western EcoSystems Technology, 

Inc. Prepared for Duke Energy. 

Taylor, K., J. Gruver, and K. Bay. 2008. Wildlife Studies for the Campbell Hill Wind Resource 

Area, Converse County, Wyoming. Western EcoSystems Technology, Inc. Prepared for 

Three Buttes Windpower, LLC and Duke Energy. 

U.S. Fish and Wildlife Service (USFWS). 2010. Species Listed in Colorado. 

http://ecos.fws.gov/tess_public/pub/stateListingAndOccurrenceIndividual.jsp?state=CO&

s8fid=112761032792&s8fid=112762573902&s8fid=24012906356871