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.

Contract No. DE-AC36-08GO28308

Avian Monitoring and Mortality 

Report at the National Wind 

Technology Center

January 2010 - February 2011

Tetra Tech EC, Inc.

Lakewood, Colorado

NREL Technical Monitor: Brenda Beatty

Subcontract Report

NREL/SR-1900-70626

June 2018
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.

Contract No. DE-AC36-08GO28308

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

Avian Monitoring and Mortality 

Report at the National Wind 

Technology Center

2010 - 2011

Tetra Tech EC, Inc.

Lakewood, Colorado

NREL Technical Monitor: Brenda Beatty

Prepared under Subcontract No(s). LGK-0-40463-01

Suggested Citation 

Tetra Tech EC. 2018. Avian Monitoring and Mortality Report at the 

National Wind Technology Center: January 2010 - February 2011. 

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

70626. https://www.nrel.gov/docs/fy18osti/70626.pdf.

Subcontract Report

NREL/SR-1900-70626

June 2018
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 

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NREL prints on paper that contains recycled content.
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Avian Monitoring and Mortality Report 

National Wind Technology Center 

ES-1 October 2011 

EXECUTIVE SUMMARY 

The National Renewable Energy Laboratory (NREL) contracted Tetra Tech EC, Inc. (Tetra 

Tech) to conduct avian monitoring and bird and bat mortality surveys at the National Wind 

Technology Center (NWTC) in 2010–2011 to quantify local avian use in the NWTC and vicinity 

and to assess potential impacts to avian and bat species associated with the wind turbines and 

associated meteorological (met) towers at NWTC. Several different types of wind turbines are 

present on the NWTC with different capacities for energy production (1 kilowatt–3 megawatts 

[MW]; varying hub heights and turbine blade lengths) and met towers (guyed and unguyed) that 

vary in height (9.1–135 meters [m]). Installation of three newer generation, multi-MW wind 

turbines (large turbines) has raised awareness regarding the potential for wildlife impacts. In a 

U.S. Department of Energy (DOE) review of the large turbine installations, DOE requested 

monitoring of avian and bat mortality be conducted, so that mitigation measures could be 

developed if impacts to avian and bat species are observed. 

To quantify local avian use in the NWTC and vicinity, Tetra Tech conducted avian point count 

surveys at 6 locations within the NWTC, as well as at reference locations in the adjacent Rocky 

Flats National Wildlife Refuge (3 locations; Rocky Flats) and the nearby Boulder County Open 

Space (3 locations; Boulder County). Further, Tetra Tech conducted breeding bird transect 

surveys to assess use of the NWTC by breeding grassland birds. To assess potential impacts to 

avian and bat species associated with the operation of wind turbines and associated met towers at 

the NWTC, Tetra Tech conducted fatality monitoring surveys at all vertical structures within the 

NWTC including observer efficiency and carcass persistence trials to refine the mortality 

estimation. It is therefore important to note when considering the results that multiple factors 

influence the probability of a species to have negative interactions with turbines, met towers, or 

guy wires, including the number of individuals at the site and the frequency that the species flies 

at rotor-swept area (RSA) height. Additionally, the relationship between avian use and mortality 

is not yet completely well-defined (NWCC 2010). Conclusions discussed below were based 

upon available data. 

POINT COUNT SURVEYS 

Non-raptor mean use was highest at the NWTC during the summer among all surveyed seasons 

(12.85 birds/20 minutes). Within the NWTC, western meadowlark, red-winged blackbird, horned 

lark, and grasshopper sparrow were among the most numerous non-raptors observed. Of these 

species, only horned larks and grasshopper sparrow were observed flying at RSA height (0.08 

and 0.03 birds flying at RSA height/20 minutes, respectively). Despite high mean use horned 

larks and grasshopper sparrows are common grassland species in the region with stable regional 

populations; thus, population-level impacts appear to be minimal because a low proportion of 

individuals were observed flying at RSA height. Additionally, common ravens were observed 

flying at RSA height but encounter rates were also low (0.05 birds flying at RSA height/20 

minutes or less). Low mean use (5.63 birds/20 minutes annual) and encounter rates (<0.05 birds 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

ES-2 October 2011 

flying at RSA height/20 minutes) across all seasons for non-raptors suggests that turbine-related 

impacts to the non-raptors using the NWTC will be low. 

Raptor mean use was highest at the NWTC during the spring and early summer among all 

surveyed seasons (0.25 birds/30 minutes and 0.29 birds/30 minutes, respectively). Raptor species 

with the highest mean use included red-tailed hawk, turkey vulture, and American kestrel. Over 

all seasons, encounter rates for raptor species were low at less than 0.05 birds flying at RSA 

height/20 min during the late summer and less than 0.05 birds flying at RSA height/30 min 

during the early summer. Raptors observed are common to the grasslands present in the region 

and low encounter rates suggest there is minimal potential for turbine-related impacts to these 

species. 

No federal or state-listed threatened or endangered species were observed during point count 

surveys. However, bald and golden eagles were observed incidental to and during point counts 

at the NWTC and at off-site locations, including an active bald eagle nest within 1.5 miles 

northeast of the NWTC. Bald and golden eagles are given federal protection by the Bald and 

Golden Eagle Protection Act (BGEPA) of 1940 (16 USC 668-668d, 54 Stat. 250) as amended. 

Colorado Department of Wildlife (CDOW) also lists bald eagles as species of concern. Both bald 

and golden eagles were observed at the Rocky Flats reference area, but no eagles were observed 

at the NWTC. As no bald eagles were observed within the NWTC and mean use off site was low 

(0.01 birds/30 min), it is unlikely that bald eagles will be negatively affected by the continued 

development of the NWTC. The undeveloped grasslands surrounding the NWTC would provide 

a large expanse of foraging habitat and the small prairie dog colony on the Boulder County 

reference area could attract golden eagles to the area; therefore, golden eagles could utilize the 

NWTC. However, given the low mean use (0.02 birds/30 min) off site and the presence of 

available foraging habitat and prey off site, it is unlikely that golden eagles will be negatively 

affected by the continued development at the NWTC. 

In addition to the bald and golden eagles, two state species of concern were observed – 

ferruginous hawk and sandhill crane. Ferruginous hawks, found throughout the year in the 

region, were observed incidentally to and during point count surveys at the NWTC, but only 

during the spring and summer seasons. There was low NWTC mean use (0.01 birds/30 min) 

during point count surveys, limited observed prey at the NWTC, and limited available foraging 

habitat with prey in Rocky Flats and Boulder County; thus, it is unlikely that ferruginous hawks 

will be negatively affected by the continued development and use of the NWTC. However, onand off-site populations of prairie dogs are currently depressed due to plague, and the prey base 

for ferruginous hawks could increase over time if these colonies are repopulated. Sandhill 

cranes, present as spring and fall migrants, were only observed during the fall season as a single 

flock of 4 individuals on November 12, 2010. In combination, low mean use (0.06 birds/20 min), 

lack of suitable roosting and foraging habitat at the NWTC, low encounter rates for all three 

large turbines (0.06 birds flying at RSA height/20 min), and no publicly available information on 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

ES-3 October 2011 

fatalities of sandhill cranes at wind energy facilities, indicate that sandhill cranes that migrate 

through the region are unlikely to be negatively affected by the NWTC. 

TRANSECT SURVEYS 

Grassland bird species observed nesting at the NWTC included western meadowlark, vesper 

sparrow, grasshopper sparrow, savannah sparrow, and horned lark. Although sample size of 

these species was limited, grassland breeding bird distribution at the NWTC does not appear to 

be affected by the wind turbines at NWTC. 

MORTALITY SURVEYS 

The fatality monitoring program established at the NWTC was designed to provide estimates of 

annual avian and bat species’ fatality rates that are comparable to the pre-construction survey 

(Schmidt et al. 2003) and publicly available post-construction surveys at other wind energy 

facilities by using methods that account for searcher efficiency and carcass persistence time. 

Based on the turbines and associated met towers at the NWTC during the 2001–2002 study, 

Schmidt et al. (2003) estimated 24 avian fatalities would occur on the NWTC annually. 

However, statistical estimators used to calculate fatalities have been improved since the preconstruction surveys of the large turbines at the NWTC. As stated by Huso (2010), “failure to 

use an unbiased estimator precludes direct comparability of results among studies and even 

within studies.” Thus, a direct comparison of the estimated number of fatalities between Schmidt 

et al. (2003) and this study cannot be completed. 

During fall/winter seasons, fatalities of 0.22 birds/study plot/7 months and fatalities of 1.45 

bats/study plot/7 months are estimated to occur on the NWTC site during these seasons. During 

spring/summer seasons, fatalities of 0.85 birds/study plot/5 months and fatalities of 1.53 

bats/study plot/5 months are estimated to occur on the NWTC site during these seasons. Annual 

fatality estimates in the Rocky Mountain region are 1.5 birds/turbine/year and 1.2 

bats/turbine/year (NWCC 2004). Confidence intervals for seasonal avian fatalities at NWTC 

(fall/winter: 0.19–0.66 birds/study plot/7 months; spring/summer 0.38–1.47 birds/study plot/5 

months) were lower than the Rocky Mountain regional estimate and fatality estimates for bats in 

the Rocky Mountain region are within the calculated confidence interval of bats/study plot/time 

period at NWTC (fall/winter: 1.15–4.43, spring/summer: 0.19–4.04). Although similar to 

regional estimates, additional installation of multi-megawatt large turbines are likely to cause an 

increase in the total site fatalities as the majority of fatalities observed during the 2010–2011 

study were found near large turbines and their associated met towers. 

 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

ES-4 October 2011 

Table ES-1. Avian Use Summary (January 13 to July 8, 2010)1 

Variable Result Details 

Non-raptors 

Mean use on the NWTC 

Winter: 0.64 birds/30 min 

Spring: 3.18 birds/30 min 

Summer: 5.53 birds/30 min 

Mean use off-site 

Winter: 1.61 birds/30 min 

Spring: 8.17 birds/30 min 

Summer: 1.33 birds/30 min 

Number of species with high encounter rates 

(>1.0 birds at RSA height/20 min) None 

Federally listed2 species observed within the NWTC None 

Federally listed species observed off-site None 

State-listed species3 within the NWTC None 

State-listed species off-site Yes Long-billed Curlew 

State-listed species observed nesting within NWTC None 

Raptors 

Mean use on the NWTC 

Winter: 0.18 birds/30 min 

Spring: 0.25 birds/30 min 

Summer: 0.29 birds/30 min 

Mean use off-site 

Winter: 0.15 birds/30 min 

Spring: 0.21 birds/30 min 

Summer: 0.25 birds/30 min 

Number of species with high encounter rates 

(>1.0 birds at RSA height/20 min) None 

Eagles observed within the NWTC None 

Eagles observed off-site Yes Golden eagle, 

Bald eagle 

Federally listed species observed within the NWTC None 

Federally listed species observed off-site None 

State-listed species within the NWTC Yes Ferruginous hawk 

State-listed species observed off-site None 

State-listed species observed nesting within the NWTC None 

State-listed species within the RSA Yes Ferruginous hawk 

Habitat 

Native habitat likely to be affected by development Yes Grassland 

Lakes (waterfowl attractant) None 

Wetlands (attractant for cranes, waterfowl, and other 

water-based species) None 

Cliffs (raptor nesting and traveling) None 

River (permanent water source, migration corridor) None 

Known refuges or habitat features that may funnel 

migrants Yes Rocky Flats NWR 

1

Summary based on 30-minute point count data collected by NREL biologists.

2

Federally listed species include species listed as endangered, threatened, or candidate species in the Endangered 

Species Act. 

3

State-listed species include species listed as endangered, threatened or species of concern by Colorado Division 

of Wildlife. 

 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

ES-5 October 2011 

Table ES-2. Avian Use Summary (July 16, 2010 to February 14, 2011)1 

Variable Result Details 

Non-raptors 

Mean use on the NWTC Summer: 12.85 birds/20 min

Fall: 3.12 birds/20 min

Winter: 1.18 birds/20 min

Mean use off-site Summer: 9.53 birds/20 min

Fall: 4.64 birds/20 min

Winter: 0.82 birds/20 min

Number of species with high encounter rates 

(>1.0 birds at RSA height/20 min) 

None

Federally listed2 species observed within the NWTC None

Federally listed species observed off-site None

State-listed species3 within the NWTC Yes Sandhill crane 

State-listed species observed nesting within NWTC None

State-listed species within RSA Yes Sandhill crane 

Raptors 

Mean use on the NWTC Summer: 0.03 birds/20 min

Fall: 0.13 birds/20 min

Winter: 0.07 birds/20 min

Mean use off-site Summer: 0.20 birds/20 min

Fall: 0.22 birds/20 min

Winter: 0.18 birds/20 min

Number of species with high encounter rates 

(>1.0 birds at RSA height/20 min) 

None

Eagles observed within the NWTC None

Eagles observed off-site Yes Golden eagle 

Federally listed species observed within the NWTC None

Federally listed species observed off-site None

State-listed species within the NWTC Yes Ferruginous hawk 

State-listed species observed off-site None

State-listed species within the RSA None

Habitat 

Native habitat likely to be affected by development Yes Grassland 

Lakes (waterfowl attractant) None

Wetlands (attractant for cranes, waterfowl, and other 

water-based species) 

None

Cliffs (raptor nesting and traveling) None

River (permanent water source, migration corridor) None

Known refuges or habitat features that may funnel 

migrants 

Yes Rocky Flats NWR 

1

Summary based on point count data collected by Tetra Tech biologists.

2

Federally listed species include species listed as endangered, threatened, or candidate species in the Endangered 

Species Act. 

3

State-listed species include species listed as endangered, threatened or species of concern by Colorado Division 

of Wildlife. 

 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

ES-6 October 2011 

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Avian Monitoring and Mortality Report 

National Wind Technology Center 

i October 2011 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY .......................................................................................................ES-1 

1. INTRODUCTION ................................................................................................................. 1-1

1.1 Background Information ................................................................................................ 1-1

1.2 Study Description ........................................................................................................... 1-3

1.3 Protected Species Information ....................................................................................... 1-4

2. AVIAN MONITORING – FIXED-POINT SURVEYS ........................................................ 2-1

2.1 Background .................................................................................................................... 2-1

2.2 Objectives ...................................................................................................................... 2-1

2.3 Methods .......................................................................................................................... 2-1

2.3.1 Fixed-point Surveys ........................................................................................... 2-1

2.3.2 Incidental Observations ..................................................................................... 2-3

2.4 Analysis .......................................................................................................................... 2-3

2.4.1 Species Groupings ............................................................................................. 2-3

2.4.2 Avian Use of the National Wind Technology Center ....................................... 2-3

2.4.3 Flight Behavior .................................................................................................. 2-3

2.4.4 Encounter Rate .................................................................................................. 2-4

2.4.5 Mortality Risk .................................................................................................... 2-4

2.5 Results ............................................................................................................................ 2-5

2.5.1 Avian Use and Frequency of Occurrence, 2010–2011 survey data .................. 2-5

2.5.2 Flight Height and Encounter Rate, 2010–2011 survey data ............................ 2-14

2.5.3 Incidental Observations, 2010–2011 Data ...................................................... 2-18

2.5.4 Protected Species, 2010-2011 Data ................................................................. 2-20

2.5.5 Comparison to Historical Data ........................................................................ 2-21

2.6 Discussion and Recommendations .............................................................................. 2-23

2.6.1 Non-Raptor Use and Encounter Rate .............................................................. 2-24

2.6.2 Raptor Use and Encounter Rate ...................................................................... 2-25

2.6.3 Comparison to Historical Data ........................................................................ 2-26

2.6.4 Protected Species ............................................................................................. 2-27

2.6.5 Recommendations ........................................................................................... 2-29

3. AVIAN MONITORING – TRANSECT SURVEYS ............................................................ 3-1

3.1 Background .................................................................................................................... 3-1

3.2 Study objectives ............................................................................................................. 3-1

3.3 Methods .......................................................................................................................... 3-1

3.4 Analysis .......................................................................................................................... 3-1

3.5 Results ............................................................................................................................ 3-2

3.6 Discussion and Recommendations ................................................................................ 3-2

3.6.1 Breeding Bird Density and Distribution ............................................................ 3-2

3.6.2 Recommendations ............................................................................................. 3-3

4. AVIAN AND BAT MORTALITY ....................................................................................... 4-1

4.1 Background .................................................................................................................... 4-1

4.2 Study objectives ............................................................................................................. 4-1
Avian Monitoring and Mortality Report 

National Wind Technology Center 

ii October 2011 

4.3 Methods .......................................................................................................................... 4-2

4.3.1 Carcass Searches ............................................................................................... 4-2

4.3.2 Observer Efficiency ........................................................................................... 4-3

4.3.3 Carcass Persistence ............................................................................................ 4-3

4.3.4 Incidental Casualties .......................................................................................... 4-4

4.4 Analysis .......................................................................................................................... 4-4

4.4.1 Carcass Searches ............................................................................................... 4-4

4.4.2 Searcher Efficiency ........................................................................................... 4-4

4.4.3 Carcass Persistence ............................................................................................ 4-4

4.4.4 Determination of Avian and Bat Mortality Estimates ....................................... 4-5

4.5 Results ............................................................................................................................ 4-6

4.5.1 Carcass Searches ............................................................................................... 4-6

4.5.2 Observer Efficiency ........................................................................................... 4-6

4.5.3 Carcass Persistence ............................................................................................ 4-7

4.5.4 Incidental Casualties .......................................................................................... 4-7

4.5.5 Protected Species ............................................................................................... 4-7

4.5.6 NWTC Avian and Bat Mortality Estimate ........................................................ 4-7

4.6 Discussion and Recommendations ................................................................................ 4-8

4.6.1 Discussion .......................................................................................................... 4-8

4.6.2 Recommendations ........................................................................................... 4-10

5. REFERENCES ...................................................................................................................... 5-1
Avian Monitoring and Mortality Report 

National Wind Technology Center 

iii October 2011 

LIST OF FIGURES 

Figure 1. NWTC Area Location Map 

Figure 2. On-site and Off-site Point Count Locations 

Figure 3a. Non-raptor mean use by survey date at the National Wind Technology 

Center, 30-minute point count surveys. 

Figure 3b. Non-raptor mean use by survey date at the National Wind Technology 

Center, 20-minute point count surveys. 

Figure 3c. Non-raptor mean use by survey date at Rocky Flats NWR and Boulder 

County Open Space, 30-minute point count surveys. 

Figure 3d. Non-raptor mean use by survey date at Rocky Flats NWR and Boulder 

County Open Space, 20-minute point count surveys. 

Figure 4a. Non-raptor mean use by point at the National Wind Technology Center, 

30-minute point count surveys. 

Figure 4b. Non-raptor mean use by point at the National Wind Technology Center, 

20-minute point count surveys. 

Figure 4c. Non-raptor mean use by point at Rocky Flats NWR and Boulder County 

Open Space, 30-minute point count surveys. 

Figure 4d. Non-raptor mean use by point at Rocky Flats NWR and Boulder County 

Open Space, 20-minute point count surveys. 

Figure 5a. Raptor mean use by survey date at the National Wind Technology Center, 

30-minute point count surveys. 

Figure 5b. Raptor mean use by survey date at the National Wind Technology Center, 

20-minute point count surveys. 

Figure 5c. Raptor mean use by survey date at Rocky Flats NWR and Boulder County 

Open Space, 30-minute point count surveys. 

Figure 5d. Raptor mean use by survey date at Rocky Flats NWR and Boulder County 

Open Space, 20-minute point count surveys. 

Figure 6a. Raptor mean use by point at the National Wind Technology Center, 30-

minute point count surveys. 

Figure 6b. Raptor mean use by point at the National Wind Technology Center, 20-

minute count surveys. 

Figure 6c. Raptor mean use by point at the Rocky Flats NWR and Boulder County 

Open Space, 30-minute point count surveys. 

Figure 6d. Raptor mean use by point at the Rocky Flats NWR and Boulder County 

Open Space, 20-minute point count surveys. 

Figure 7. Palmer Drought Severity Index (PDSI) for Colorado Platte Drainage 

Basin, including the National Wind Technology Center, from January 

2000 to May 2011. 

Figure 8. Breeding Bird Transects and Grassland Bird Locations 

Figure 9. NWTC Vertical Structures and Carcass Search Plots 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

iv October 2011 

Figure 10. Carcass Persistence Trial Location 

Figure 11. Locations of Found Fatalities in Relation to Vertical Structures 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

v October 2011 

LIST OF TABLES 

Table ES-1. Avian Use Summary (January 13 to July 8, 2010). 

Table ES-2. Avian Use Summary (July 16, 2010 to February 14, 2011). 

Table 1a. National Wind Technology Center 30-minute point count survey dates. 

Table 1b. National Wind Technology Center 20-minute point count survey dates. 

Table 2a. Avian species observed during 30-minute point count surveys at the 

National Wind Technology Center, 2010. 

Table 2b. Avian species observed during 20-minute point count surveys at the 

National Wind Technology Center, 2010-2011. 

Table 2c. Avian species observed during 30-minute point count surveys at off-site 

reference locations, 2010. 

Table 2d Avian species observed during 20-minute point count surveys at off-site 

reference locations, 2010-2011. 

Table 3a. Avian mean use, by species group, observed during 30-minute point count 

surveys at the National Wind Technology Center, 2010. 

Table 3b. Avian mean use, by species group, observed during 20-minute point count 

surveys at the National Wind Technology Center, 2010-2011. 

Table 3c. Avian mean use, by species group, observed during 30-minute point count 

surveys at off-site reference locations, 2010. 

Table 3d. Avian mean use, by species group, observed during 20-minute point count 

surveys at off-site reference locations, 2010-2011. 

Table 4a. Avian species observed by point during Winter 2010 30-minute point 

count surveys at the National Wind Technology Center. 

Table 4b. Avian species observed by point during Spring 2010 30-minute point 

count surveys at the National Wind Technology Center. 

Table 4c. Avian species observed by point early Summer 2010 30-minute point 

count surveys at the National Wind Technology Center. 

Table 4d. Avian species observed by point during late Summer 2010 20-minute 

point count surveys at the National Wind Technology Center. 

Table 4e. Avian species observed by point during Fall 2010 20-minute point count 

surveys at the National Wind Technology Center. 

Table 4f. Avian species observed by point during Winter 2010-2011 20-minute 

point count surveys at the National Wind Technology Center. 

Table 4g. Avian species observed by point during Winter 2010 30-minute point 

count surveys at off-site reference locations. 

Table 4h. Avian species observed by point during Spring 2010 30-minute point 

count surveys at off-site reference locations. 

Table 4i. Avian species observed by point during early Summer 2010 30-minute 

point count surveys at off-site reference locations. 

Table 4j. Avian species observed by point during late Summer 2010 20-minute 

point count surveys at off-site reference locations 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

vi October 2011 

Table 4k. Avian species observed by point during Fall 2010 20-minute point count 

surveys at off-site reference locations. 

Table 4l. Avian species observed by point during Winter 2010-2011 20-minute 

point count surveys at off-site reference locations. 

Table 5a. Summary of avian flight heights (includes flying birds only) in relation to 

the 1.5-MW turbine rotor-swept area (RSA) during 30-minute point count 

surveys at the National Wind Technology Center, 2010. 

Table 5b. Summary of avian flight heights (includes flying birds only) in relation to 

the 1.5-MW turbine rotor-swept area (RSA) during 20-minute point count 

surveys at the National Wind Technology Center, 2010-2011. 

Table 5c. Summary of avian flight heights (includes flying birds only) in relation to 

the 2.3-MW turbine rotor-swept area (RSA) during 30-minute point count 

surveys at the National Wind Technology Center, 2010. 

Table 5d. Summary of avian flight heights (includes flying birds only) in relation to 

the 2.3-MW turbine rotor-swept area (RSA) during 20-minute point count 

surveys at the National Wind Technology Center, 2010-2011. 

Table 5e. Summary of avian flight heights (includes flying birds only) in relation to 

the 3.0-MW turbine rotor-swept area (RSA) during 30-minute point count 

surveys at the National Wind Technology Center, 2010. 

Table 5f. Summary of avian flight heights (includes flying birds only) in relation to 

the 3.0-MW turbine rotor-swept area (RSA) during 20-minute point count 

surveys at the National Wind Technology Center, 2010-2011. 

Table 6a. Avian flight height characteristics in relation to the 1.5-MW turbine rotorswept area (RSA) during Winter 2010 30-minute point count surveys at 

the National Wind Technology Center. 

Table 6b. Avian flight height characteristics in relation to the 1.5-MW turbine rotorswept area (RSA) during Spring 2010 30-minute point count surveys at 

the National Wind Technology Center. 

Table 6c. Avian flight height characteristics in relation to the 1.5-MW turbine rotorswept area (RSA) during early Summer 2010 30-minute point count 

surveys at the National Wind Technology Center. 

Table 6d. Avian flight height characteristics in relation to the 1.5-MW turbine rotorswept area (RSA) during late Summer 2010 20-minute point count surveys 

at the National Wind Technology Center. 

Table 6e. Avian flight height characteristics in relation to the 1.5-MW turbine rotorswept area (RSA) during Fall 2010 20-minute point count surveys at the 

National Wind Technology Center. 

Table 6f. Avian flight height characteristics in relation to the 1.5-MW turbine rotorswept area (RSA) during Winter 2010-2011 20-minute point count 

surveys at the National Wind Technology Center. 

Table 6g. Avian flight height characteristics in relation to the 2.3-MW turbine rotorswept area (RSA) during Winter 2010 30-minute point count surveys at 

the National Wind Technology Center. 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

vii October 2011 

Table 6h. Avian flight height characteristics in relation to the 2.3-MW turbine rotorswept area (RSA) during Spring 2010 30-minute point count surveys at 

the National Wind Technology Center. 

Table 6i. Avian flight height characteristics in relation to the 2.3-MW turbine rotorswept area (RSA) during early Summer 2010 30-minute point count 

surveys at the National Wind Technology Center. 

Table 6j. Avian flight height characteristics in relation to the 2.3-MW turbine rotorswept area (RSA) during late Summer 2010 20-minute point count surveys 

at the National Wind Technology Center. 

Table 6k. Avian flight height characteristics in relation to the 2.3-MW turbine rotorswept area (RSA) during Fall 2010 20-minute point count surveys at the 

National Wind Technology Center. 

Table 6l. Avian flight height characteristics in relation to the 2.3-MW turbine rotorswept area (RSA) during Winter 2010 20-minute point count surveys at 

the National Wind Technology Center. 

Table 6m. Avian flight height characteristics in relation to the 3.0-MW turbine rotorswept area (RSA) during Winter 2010 30-minute point count surveys at 

the National Wind Technology Center. 

Table 6n. Avian flight height characteristics in relation to the 3.0-MW turbine rotorswept area (RSA) during Spring 2010 30-minute point count surveys at 

the National Wind Technology Center. 

Table 6o. Avian flight height characteristics in relation to the 3.0-MW turbine rotorswept area (RSA) during early Summer 2010 30-minute point count 

surveys at the National Wind Technology Center. 

Table 6p. Avian flight height characteristics in relation to the 3.0-MW turbine rotorswept area (RSA) during late Summer 2010 20-minute point count surveys 

at the National Wind Technology Center. 

Table 6q. Avian flight height characteristics in relation to the 3.0-MW turbine rotorswept area (RSA) during Fall 2010 20-minute point count surveys at the 

National Wind Technology Center. 

Table 6r. Avian flight height characteristics in relation to the 3.0-MW turbine rotorswept area (RSA) during Winter 2010-2011 20-minute point count 

surveys at the National Wind Technology Center. 

Table 7a. Incidental observations of birds during 30-minute point count surveys at 

the National Wind Technology Center and off-site reference locations, 

2010. 

Table 7b. Incidental observations of birds during 20-minute point count surveys at 

the National Wind Technology Center, 2010-2011. 

Table 7c. Incidental observations of birds during 20-minute point count surveys at 

Boulder County, 2010-2011. 

Table 7d. Incidental observatinos of birds during 20-minute point counts at Rocky 

Flats, 2010-2011 
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Table 8a. Non-raptor species observed by point during 10-minute point count 

surveys at the National Wind Technology Center, Winter 2010. 

Table 8b. Non-raptor species observed by point during 10-minute point count 

surveys at the National Wind Technology Center, Spring 2010. 

Table 8c. Non-raptor species observed by point during 10-minute point count 

surveys at the National Wind Technology Center, Summer 2010. 

Table 8d. Non-raptor species observed by point during 10-minute point count 

surveys at the National Wind Technology Center, Fall 2010. 

Table 8e. Avian species observed by point during 10-minute point count surveys at 

the National Wind Technology Center, Winter 2010-2011. 

Table 8f. Non-raptor species observed by point during 10-minute point count 

surveys at the National Wind Technology Center from 01/13/2010 through 

02/14/2011. 

Table 8g. Non-raptor species observed by point during 10-minute point count 

surveys at off-site reference locations, Winter 2010. 

Table 8h. Non-raptor species observed by point during 10-minute point count 

surveys at off-site reference locations, Spring 2010. 

Table 8i. Non-raptor species observed by point during 10-minute point count 

surveys at off-site reference locations, Summer 2010. 

Table 8j. Non-raptor species observed by point during 10-minute point count 

surveys at off-site reference locations, Fall 2010. 

Table 8k. Non-raptor species observed by point during 10-minute point county 

surveys at off-site reference locations, Winter 2010-2011. 

Table 8l. Non-raptor species observed by point during 10-minute point count 

surveys at off-site reference locations from 01/13/2010 through 

02/14/2011 

Table 9. Bootstrapped searcher efficiency (probability that a carcass is found) and 

carcass persistence (days) estimates and 90 percent confidence intervals 

(CI). 

Table 10. Bootstrapped fatality estimates and 90 percent confidence intervals 

derived using the Huso Estimator. 
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ix October 2011 

LIST OF APPENDICES 

Appendix 1a. Flight directions of birds observed during Winter 2010 30-minute point 

count surveys at the National Wind Technology Center. 

Appendix 1b. Flight directions of birds observed during Spring 2010 30-minute point 

count surveys at the National Wind Technology Center. 

Appendix 1c. Flight directions of birds observed during late Summer 2010 20-minute 

point count surveys at the National Wind Technology Center. 

Appendix 1d. Flight directions of birds observed during Fall 2010 20-minute point count 

surveys at the National Wind Technology Center. 

Appendix 1e. Flight directions of birds observed during Winter 2010-2011 20-minute 

point count surveys at the National Wind Technology Center. 

Appendix 1f. Flight directions of birds observed during Winter 2010 30-minute point 

count surveys at off-site reference locations. 

Appendix 1g. Flight directions of birds observed during Spring 2010 30-minute point 

count surveys at off-site reference locations. 

Appendix 1h. Flight directions of birds observed during early Summer 2010 30-minute 

point count surveys at the off-site reference locations. 

Appendix 2a. Avian percent composition and frequency, sorted by species group, 

observed during 30-minute point count surveys at the National Wind 

Technology Center, 2010. 

Appendix 2b. Avian percent composition and frequency, sorted by species group, 

observed during 20-minute point count surveys at the National Wind 

Technology Center, 2010-2011. 

Appendix 2c. Avian percent composition and frequency, sorted by species group, 

observed during 30-minute point count surveys at off-site reference 

locations, 2010. 

Appendix 2d. Avian percent composition and frequency, sorted by species group, 

observed during 20-minute point count surveys at off-site reference 

locations, 2010-2011. 
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LIST OF ACRONYMS AND ABBREVIATIONS 

BGEPA Bald and Golden Eagle Protection Act 

Boulder County Boulder County Open Space 

CDOW Colorado Division of Wildlife 

CI Confidence Interval 

CRP Conservation Reserve Program 

DOE U.S. Department of Energy 

ESA Endangered Species Act 

GPS Global Positioning System 

km kilometer 

kW kilowatt 

m meters 

MBTA Migratory Bird Treaty Act 

met meteorological 

min minutes 

MW megawatt 

NEPA National Environmental Policy Act 

NREL National Renewable Energy Laboratory 

NWR National Wildlife Refuge 

NWTC National Wind Technology Center 

PDSI Palmer Drought Severity Index 

PV photovoltaic 

Rocky Flats Rocky Flats National Wildlife Refuge 

RSA rotor-swept area 

Tetra Tech Tetra Tech EC, Inc. 

USFWS U.S. Fish and Wildlife Service 

 
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1. INTRODUCTION 

1.1 BACKGROUND INFORMATION 

Wind energy provides a clean, renewable energy source that is in high demand. As wind power 

has become more common, the need to address potential environmental impacts has increased. 

Birds have been identified as a group potentially at risk because of collisions with wind turbines 

and power lines and displacement due to the presence of the associated structures (Erickson et al. 

2005, Drewitt and Langston 2006, Arnett et al. 2007). Specifically, migrant passerines (i.e., 

songbirds) are found more often in post-construction mortality monitoring compared to other 

groups of birds (Arnett et al. 2007). At newer generation wind energy facilities outside of 

California, approximately 80 percent of documented mortalities have been songbirds, of which 

50 percent are often nocturnal migrants (Erickson et al. 2001, Drewitt and Langston 2006, 

Johnson et al. 2002, Strickland and Morrison 2008). Information from radar data and mortality 

monitoring suggest that less than 0.01 percent of migrant songbirds that pass over wind farms are 

killed (Erickson 2007). Locally breeding songbirds may experience lower mortality rates than 

migrants because many of these species tend not to fly at turbine heights during the breeding 

season. However, some breeding songbird species have behaviors that increase the risk of 

collisions with turbines. For example, horned larks have been commonly found as fatalities at 

wind farms (Erickson et al. 2002). Mortality may be partially attributed to the breeding flight 

displays in which male horned lark fly to heights of 80 meters (m) to 250 m (Pickwell 1931). 

Despite the observation that most wind farm fatalities are songbirds, raptor mortality historically 

has received the most attention as raptors are slow-reproducing, long-lived species. Raptor 

mortality at newer generation wind farms has been low relative to previous generation wind 

farms due to changes in turbine design such as tower structure (lattice to tubular) and larger 

turbines allowing for greater spacing between turbines, although there is substantial regional 

variation (Erickson et al. 2002, 2004; Johnson et al. 2002; Kerns and Kerlinger 2004; Jain et al. 

2007; NWCC 2010). Average raptor fatality rates at newer generation wind projects were 

estimated at 0.04 raptors/megawatt (MW)/year compared to older generation wind projects with 

raptor fatalities estimated at 1.37 raptors/MW/year (NWCC 2004). Although raptor mortality is 

reduced at newer generation facilities, mortality may not be eliminated by advances in turbine 

technology (e.g., turbine height, tower structure) and local micro-siting and site evaluation 

efforts are still necessary. 

In addition to avian mortality associated with wind farms, concerns have been raised that indirect 

effects from wind turbines could also be influencing local avian populations. These concerns 

include avoidance of areas near turbines by avian species after the wind farm is in operation and 

the potential for a decrease in the local avian population (Drewitt and Langston 2006, Erickson et 

al. 2007b). For example, at the Buffalo Ridge wind energy facility in Minnesota, densities of 

male songbirds were significantly lower in Conservation Reserve Program (CRP) grasslands 

containing turbines than in CRP grasslands without turbines. It was suggested that the reduced 
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density may be due to avoidance of turbine noise and maintenance activities, and reduced habitat 

quality due to the presence of access roads and large gravel pads surrounding the turbines (Leddy 

et al. 1999). Reduced abundance of grassland songbirds was found within 50 m of a turbine pad 

for a wind farm in Washington and Oregon, but the investigators attributed displacement to the 

direct loss of habitat or reduced habitat quality and not the presence of the turbines (Erickson et 

al. 2004). Recent research at two sites in North and South Dakota (Shaffer and Johnson 2008) 

suggests that certain grassland songbird species (2 of 4 species studied) may avoid turbines by as 

much as 200 m but these results have not been finalized nor verified at additional sites. None of 

these studies have addressed whether or not these avoidance effects are temporary (i.e., the birds 

may habituate to the presence of turbines over time) or permanent. 

In addition to bird mortality and displacement, bat mortality associated with wind turbine 

operation has been reported at locations around the world, including multiple wind farms in the 

United States (Durr and Bach 2004, Kunz et al. 2007, Arnett et al. 2008). The direct causes of 

bat mortality include collision with moving turbine blades (Horn et al. 2008) and pulmonary 

barotrauma (i.e., damage to lung tissue resulting from rapid changes in air pressure experienced 

when a bat flies through a field of low air-pressure near spinning blades as described in Baerwald 

et al. [2008]). Recent studies indicate that approximately half of all turbine-related bat fatalities 

result from barotrauma-related injuries rather than direct collision with turbine blades (Baerwald 

et al. 2008). These findings bring into question the number of bats fatally injured by barotrauma, 

the proportion that do not immediately succumb to injuries, and the effect this might have on 

mortality estimates, which could lead to underestimates (NWCC 2010). The indirect causal 

factors influencing bat mortality are poorly understood, and although it is generally accepted that 

certain bats (e.g., the migratory tree bats) are attracted to turbines, the reasons for attraction have 

not yet been clearly identified (Arnett et al. 2008). The current leading hypotheses are that bats 

are attracted to turbines as potential roosting locations (Kunz et al. 2007), as potential pairing or 

mating stations (Cryan and Barclay 2009), or that they are attracted to an accumulation of 

migratory insects around turbine rotors (Rydell et al. 2010). 

Two general patterns of fatalities are consistent across nearly all wind energy facilities in North 

America: (1) migratory tree-roosting bats represent the majority of fatalities (73 percent per 

Kunz et al. [2007]), and (2) the majority of bat fatalities occur during late summer and early fall, 

coinciding with the fall migratory movements of bats (Arnett et al. 2008). Impacts to bat 

populations are not easily determined because the parameters needed to model populations such 

as survival, productivity, and baseline population size are not available for many species. Efforts 

are being made to establish population databases for bats similar to those available for birds 

(USGS 2011); however, the inherent difficulties in assessing bat populations has resulted in 

limited utility of such datasets at present (O’Shea and Bogan 2003). The most reliable 

assessments of bat population trends are of colonial cave-roosting bats, particularly in the eastern 

United States where bats form large colonies in predictable locations during hibernation. 

However, population metrics for the species of bats most likely to be impacted by wind energy, 
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the migratory tree-roosting bats, are especially difficult to estimate (Carter et al. 2003, Cryan 

2003). For these reasons, it is not feasible to accurately quantify or estimate the impacts to bat 

populations, particularly those species most likely impacted by wind energy. 

1.2 STUDY DESCRIPTION 

The National Wind Technology Center (NWTC), located in Jefferson County, Colorado, 

approximately 8 miles south of Boulder, Colorado, is part of the National Renewable Energy 

Laboratory (NREL), and serves as NREL’s primary site for the development of wind energy 

technologies (Figure 1). The NWTC is located in the High Plains Ecoregion of Colorado and the 

Front Range Fans subregion (Chapman et al. 2006). The vegetation of the Front Range Fans 

subregion was historically shortgrass and mixedgrass prairie, which was comprised of blue 

grama (Bouteloua gracilis), needle and thread (Hesperostipa comata), western wheatgrass 

(Pascopyrum smithii), buffalograss (Bouteloua dactyloides), Junegrass (Koeleria macrantha), 

and little bluestem (Schizachyrium scoparium). The NWTC site contains such grasslands and 

small patches of ponderosa pine (Pinus ponderosa), as well as shrubs such as hawthorn 

(Crataegus sp.) and snowberry (Symphoricarpos albus). 

NREL contracted Tetra Tech EC, Inc. (Tetra Tech) to conduct avian monitoring and mortality 

surveys at the NWTC in 2010–2011 to quantify local avian use in the NWTC and vicinity and to 

assess potential impacts to avian and bat species from operation of the wind turbines and the 

associated meteorological (met) towers at NWTC. Several different types of wind turbines are 

present on the NWTC with different capacities for energy production (1 kilowatt [kW]–3 

megawatts [MW]; varying hub heights and turbine blade lengths) and met towers (guyed and 

unguyed) that vary in height (9.1–135 m). Installation of three new generation, multi-MW wind 

turbines (large turbines) has raised awareness regarding the potential for wildlife impacts. In a 

U.S. Department of Energy (DOE) National Environmental Policy Act (NEPA) review of the 

large turbine installations, DOE requested that monitoring of avian and bat mortality be 

conducted, so that mitigation measures could be developed if impacts to avian and bat species 

are observed. 

As the NWTC functions as testing facility for the development and improvement of wind 

technology, it is an appropriate location in which to collect information to address the recent 

industry awareness regarding the potential for wildlife impacts. Previous information regarding 

avian use of the facility and reference sites and mortality estimates were documented during a 

study in 2001–2002 by Schmidt et al. (2003) and results from the 2001–2002 study are cited in 

this report for comparison. 

This project is comprised of three components designed to enhance the understanding of avian 

use and distribution at the NWTC and the vicinity, and impacts to avian and bat species 

associated with wind turbines and met towers (based on study protocols developed by WEST 

[2009]): 
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 avian point count surveys; 

 breeding bird transect surveys; and 

 avian and bat mortality surveys. 

1.3 PROTECTED SPECIES INFORMATION 

The Endangered Species Act (ESA), as administered by the USFWS, mandates protection of 

species federally listed as threatened or endangered and their associated designated critical 

habitat. The ESA makes it unlawful to “take” a listed species. Take is defined as “to harass, 

harm, pursue, hunt, shoot, wound, kill, trap, capture or collect or attempt to engage in any such 

conduct” (USFWS 2011). USFWS lists two threatened species (Mexican spotted owl and piping 

plover) and one endangered species (least tern) as potentially occurring within Jefferson County 

(2011b). No candidate species are listed for Jefferson County. 

In addition to federal listing, most states also list species that are declining and in danger of 

becoming extinct within the state’s border. The Colorado Division of Wildlife (CDOW; now 

Colorado Parks and Wildlife) lists eight avian species as threatened or endangered within the 

state boundary – burrowing owl, least tern, Mexican spotted owl, piping plover, plains sharptailed grouse, lesser prairie chicken, southwestern willow flycatcher, and whooping crane 

(CDOW 2010). However, lists are not provided for the county level. Based on species’ range, 

burrowing owl (state threatened) could occur in Jefferson County. In addition to federal and state 

listed threatened and endangered species, CDOW also maintains a list of species of concern for 

non-game species based on population trend, population size, and habitat rarity in an attempt to 

provide conservation measures to keep species from becoming threatened or endangered; 

however, this is not a statutory category (CDOW 2010). Eleven avian species are designated as 

species of concern by CDOW – American peregrine falcon, bald eagle, Columbian sharp-tailed 

grouse, ferruginous hawk, greater sage-grouse, sandhill crane, Gunnison sage-grouse, long-billed 

curlew, mountain plover, western snowy plover, and western yellow-billed cuckoo (CDOW 

2010). Based on species’ range, peregrine falcon, bald eagle, ferruginous hawk, sandhill crane, 

long-billed curlew, and mountain plover could occur in Jefferson County. 

The Bald and Golden Eagle Protection Act (BGEPA) prohibits the take of any bald or golden 

eagle, alive or dead, including any part, nest, or egg. “Take” is defined as “pursue, shoot, shoot 

at, poison, wound, kill, capture, trap, collect, molest or disturb” a bald or golden eagle. “Disturb” 

means to agitate or bother an eagle to a degree that causes, or is likely to cause (1) injury to an 

eagle; (2) a decrease in its productivity, by substantially interfering with normal breeding, 

feeding, or sheltering behavior; or (3) nest abandonment, by substantially interfering with normal 

breeding, feeding, or sheltering behavior. 

Additionally, the USFWS has listed 45 species of concern for USFWS Region 6 (USFWS 

2008a). These species are not protected under the ESA, but are protected, as are other native 
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migratory birds, under the Migratory Bird Treaty Act (MBTA) of 1918. Under the MBTA it is 

unlawful to pursue, hunt, take, capture or kill; attempt to take, capture or kill; possess, offer to or 

sell, barter, purchase, deliver or cause to be shipped, exported, imported, transported, carried or 

received any migratory bird, part, nest, egg or product. Despite extensive liability provisions, the 

USFWS has narrowly interpreted its permitting authority. As currently written, USFWS’s 

regulations establish a permitting scheme for a variety of intentional activities, such as hunting, 

falconry, certain import and export activities, depredation control, and scientific research. 

However, currently “there is no permitting scheme for the incidental take of migratory birds 

during otherwise lawful activities” (Beveridge 2005). 
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2. AVIAN MONITORING – FIXED-POINT SURVEYS 

2.1 BACKGROUND 

Colorado has more than 490 documented bird species (CFO 2011) and is situated within the 

Central Flyway, one of the main bird migratory routes in North America (USFWS 2008b). The 

Central Flyway runs through the central portion of the United States and, as a consequence, the 

NWTC. Most birds that move along the Central Flyway travel from Canada through the central 

states, eventually reaching the tropics of South America via the Gulf of Mexico (USFWS 

2008b). 

2.2 OBJECTIVES 

Standardized protocols for pre-construction point counts at the NWTC had previously been 

established (Schmidt et al. 2003) and similar protocols were used in this study (WEST 2009). 

Data collected from these counts are used to identify species or species groups that may be at 

risk from NWTC operations and development. Tetra Tech estimated seasonal and spatial use of 

the NWTC and off-site reference locations (Boulder County Open Space [Boulder County] and 

Rocky Flats national Wildlife Refuge [Rocky Flats]), compared seasonal and spatial use between 

survey locations in 2010–2011, and compared 2010–2011 seasonal and spatial use to past 

surveys conducted at the same locations in 2001–2002 (Schmidt et al. 2003). Tetra Tech assessed 

potential risk to avian species present at the NWTC in relation to the recently installed three 

large turbines at the NWTC facility. 

2.3 METHODS 

Results in this report are presented in terms of species groups, and highlight federal and statelisted species, and species of concern. 

2.3.1 Fixed-point Surveys 

In 2001 to 2002, fixed-point count locations were established for monitoring avian use on site at 

the NWTC and at off-site reference locations (Rocky Flats and Boulder County; Schmidt et al. 

2003). From January 2010 to March 2011, 12 of these established point count locations were resurveyed (Figure 2), including 6 locations at the NWTC and 6 reference locations (3 locations at 

Rocky Flats, and 3 locations at Boulder County). The 12 point count locations are designated in 

this report as follows: NWTC locations are NW-01 to NW-06, Rocky Flats locations are RF-01 

to RF-03, and Boulder County locations are CB-01 to CB-03. Thirty-minute (min) fixed-point 

count surveys were conducted by NWTC staff in 2010 in late winter (January 13 to March 17), 

spring (March 26 to June 17), and early summer (June 23 to July 8) (Table 1a). For these 

surveys, NREL biologists recorded non-raptors out to 100 meters (m) for the first 10 min and 

raptors out to 200 m for 30 min based on the protocol utilized by Schmidt et al. (2003). 

Tetra Tech continued the fixed-point surveys in late summer 2010, using the 100-m and 200-m 

survey circles for non-raptors and raptors respectively, and the 30-min survey periods, but 
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recorded non-raptors during the entire 30-min period. During August 2010, the length of the 

survey period was reduced to 20 min to be consistent with the industry standard being used at 

most wind energy projects in the United States and the surveyors continued to document nonraptors observed within 100 m in the first 10 min. Tetra Tech biologists conducted point count 

surveys every week during summer 2010 (July 16 to August 27) and fall 2010 (September 2 to 

November 18), then every other week during winter 2010–2011 (December 7 to February14) 

(Table 1b). 

Data collected after July 15 but prior to the change to the 20-min survey protocol were “clipped” 

to 20 min for raptors and 10 min for non-raptors, using the recorded time of each observations. 

Clipped data, that is raptor observations from 20 to 30 min of the survey period, and non-raptor 

observations from 10 to 30 min of the survey period, were not retained in the quantitative 

analysis but were considered incidental observations (Section 2.3.2). For the 30-min data 

collected before July 15, 2010, times for observations were not recorded and therefore, these data 

could not be “clipped” to 20-minutes. Consequently it was not feasible to combine data 

collected before July 15 with data collected after July 15; therefore, these datasets were analyzed 

separately. 

The survey protocol used in the fixed-point survey is designed to collect data on all bird species 

and to provide results that are comparable with other studies at wind farms rather than to target 

specific taxa. The benefit of using this protocol is that it estimates avian use throughout the day 

and captures activity by a variety of bird species. During the breeding season, and to a lesser 

extent in the fall and winter, songbirds are most active in the morning and can be difficult to 

detect during the afternoon. In contrast, raptors become active as the sunlight heats the air and 

creates thermals, which individuals use for soaring (Ballam 1984). Thus, raptors are more readily 

detected several hours after sunrise. Therefore, this protocol is appropriate for characterizing the 

bird community using the NWTC throughout the year. 

Detectability varies among species and potentially not all individuals within the 200-m radius 

were counted. This variation in detectability results in an overestimate of mean use for 

conspicuous species and an underestimate of mean use for reclusive species (Thompson 2002). 

Birds not easily identifiable, such as those seen under low light conditions or small birds seen at 

a distance, were identified to the lowest taxonomic level possible. Hence, unidentified birds are 

included in the results. Birds that could not be identified to species were reported as “unknown.” 

Biologists continuously recorded any visual or auditory observations during point count surveys 

to evaluate avian use, behavior, and species composition. Biologists recorded the following data: 

species, number of individuals, time of observation, height aboveground, behavior, and flight 

direction. Data on flight direction can be found in Appendices 1a-h. The biologists estimated 

flight heights and distances using existing met towers, wind turbines, buildings, and topographic 

maps for reference. 
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2.3.2 Incidental Observations 

Incidental observations included observations that occurred 1) during travel between points, 2) 

before or after the official 20-min/30-min survey period, and 3) outside of the 200-m radius 

circular plot. The biologists recorded these observations on separate data sheets and these data 

were not used in the formal analysis; however, a summary of incidental birds is presented to 

provide additional information about species found in the local area and flight heights. As 

discussed in Section 2.3.1, “clipped” data were included as incidental observations. 

2.4 ANALYSIS 

2.4.1 Species Groupings 

Tetra Tech considered two primary groups of interest: non-raptors and raptors. Non-raptors were 

defined as all other avian species. Tetra Tech defined raptors as vultures, hawks, eagles, falcons, 

and owls. 

2.4.2 Avian Use of the National Wind Technology Center 

Tetra Tech derived avian use (mean use) of the NWTC by calculating the average number of 

birds observed per 20-min survey at each point, beginning with surveys conducted by Tetra Tech 

in late July 2010. To evaluate the diversity and composition of avian species using the NWTC, 

Tetra Tech first summarized the number of individuals (birds/20 min) and number of species. 

Tetra Tech also calculated a measure of variability (90 percent confidence intervals) for all mean 

use values. In addition, the number of observations is also presented, where an observation can 

be either an individual bird or a discrete flock of birds. This information helps evaluate whether 

high mean use is driven by a single event (e.g., a large flock of birds moving through the NWTC 

on migration). Because individual birds are not uniquely marked and identified, actual 

population size or abundance cannot be determined. One individual may be counted multiple 

times during a survey period or across survey periods. Therefore, avian mean use does not equate 

to abundance. 

2.4.3 Flight Behavior 

Tetra Tech evaluated flight behavior by calculating the proportion of flying birds observed 

below, within, or above the height of the turbine rotor-swept area (RSA) of the three large 

turbines. Three large turbines of varying capacity for electricity generation are installed at the 

NWTC; therefore, these three turbine heights and rotor diameter were used to calculate the RSA. 

The 1.5-MW turbine had a hub height of 80 m and rotor diameter 77 m with a calculated RSA 

between 41 and 118.5 m above ground. The 2.3-MW turbine had a hub height of 80 m and rotor 

diameter 101 m with a calculated RSA between 29.5 and 130.5 m above ground. The 3.0-MW 

turbine had a hub height of 90 m and rotor diameter 100 m with a calculated RSA between 40 

and 140 m above ground. Tetra Tech considered a bird to have flown within the height of the 

RSA if any of its recorded heights fell within the upper or lower limits of the RSA.
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2.4.4 Encounter Rate 

To estimate the rate at which a species flew at the height of the anticipated RSA, Tetra Tech 

applied the following equation to every species observed in the NWTC: 

Encounter Rate = A*Pf*Pt

A is the mean number of birds/20 min for a given species, Pf is the proportion of all activity 

observations for a given species that were flying; and Pt is the proportion of flying observations 

for a given species that were at the height of a turbine RSA. The encounter rate provides 

information on the rate at which a species may move at a height that is consistent with the RSA 

of installed turbines. This encounter rate calculation varies slightly from the study plan as this 

calculation includes all birds that flew within height of RSA not just those whose first height was 

within the RSA (WEST 2009). This updated calculation provides a more detailed assessment of 

species that may be at risk of collision. This information is an important component in evaluating 

risk of collisions; however, this number alone does not indicate risk to a species. Species with a 

high encounter rate are at a higher risk of collision than species with a low encounter rate, but it 

does not mean that mortality is certain. Other factors such as turbine location or a species ability 

to detect turbine blades, flight maneuverability, and habitat selection also influence mortality 

(Orloff and Flannery 1992). Values are sensitive to large flocks of birds flying within the RSA; 

that is, a species will have a high encounter rate even if only seen a few times in large flying 

flocks. Encounter rate also does not account for migrating behavior of nocturnal migrants. Tetra 

Tech has analyzed all monitoring and mortality data during the 2010–2011 surveys. Because all 

fatalities (see Section 4.0) were found under large turbines and met towers of similar height, 

encounter rates were calculated for only the large turbines. 

2.4.5 Mortality Risk 

The relationship between avian use and post-construction mortality is not yet completely defined 

due to a lack of pre- and post-construction data from sites with moderate to high use. Based on 

the available data from North America, raptor fatality rates generally are low at most wind 

energy developments with exceptions demonstrated at certain facilities in California with a 

predominance of older generation turbines (NWCC 2010). The highly regional nature of avian 

mean use across North America and the scarce data on avian mortality at wind farms in many 

parts of the continent contribute to uncertainty in predicting fatality rates (Arnett et al. 2007). To 

date, the most comprehensive source of regional information on avian fatality rates is the Avian 

and Bat Fact Sheet, which shows that estimated fatalities range from 14 birds/MW/yr in 

Tennessee to 0 birds/MW/yr in Oklahoma (NWCC 2010). As a result of uncertainty in predicting 

fatality rates, Tetra Tech did not derive mortality estimates from mean use data but will highlight 

those species or groups that may experience mortality or displacement that could significantly 

affect local or regional populations, based on the data provided in this report and other 

information sources. 
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2-5 October 2011 

2.5 RESULTS 

2.5.1 Avian Use and Frequency of Occurrence, 2010–2011 survey data 

Total numbers of species and individuals varied by season at the NWTC and the off-site point 

count locations. Additional information on avian use and frequency of occurrence for species 

observed during point count surveys are available in Appendices 2a-d. 

Winter 2010 (January 13–March 17) 

NWTC 

A total of 49 birds from 11 species were observed during winter 2010 at point locations within 

the NWTC (Table 2a). Overall avian mean use in winter 2010 was 0.82 birds/30 min (Table 2a). 

Overall mean use in winter 2010 by non-raptors was 0.63 birds/30 min (range: 0–8 

individuals/survey). Among non-raptor species groups observed in winter 2010, mean use was 

highest for songbirds (0.58 birds/30 min [range: 0–8 individuals/survey]; Table 3a). Species with 

the highest mean use for this species group were black-billed magpie (0.15 birds/30 min; range: 

0–3 individuals/survey) and mountain bluebird (0.13 birds/30 min [range: 0–8 

individuals/survey]; Table 3a). All other songbird species had mean use values of equal to or less 

than 0.07 birds/30 min. The woodpecker species group was the only other non-raptor group that 

had observations and had a mean use of 0.05 birds/30 min (range: 0–2 individuals/survey; Table 

3a). 

Non-raptor mean use was highest on March 17 (3.33 birds/30 min; Figure 3a). Mean use for nonraptors was highest at NW-01 (1.70 birds/30 min; Figure 4a) and observations at this point 

included black-billed magpie (4 individuals), black-capped chickadee (4 individuals), downy 

woodpecker (3 individuals) and American robin (3 individuals; Table 4a). Habitat at NW-01 

includes grasslands, which is not unique within the NWTC, and a small portion of pine forest. 

Overall mean use for raptors was 0.18 birds/30 min (range: 0–2 individuals/survey; Table 3a). 

Among the species groups observed in winter 2010, the raptor species group had the second 

highest mean use. Three raptor species were observed during winter 2010: red-tailed hawk (0.12 

birds/30min; range: 0–2 individuals/survey), American kestrel (0.05 birds/30 min; range: 0–1 

individuals/survey) and the rough-legged hawk (0.02 birds/30 min; range: 0–1 

individuals/survey; Table 3a). 

Mean use by raptors was highest on January 29 (0.67 birds/30 min; Figure 5a). All other survey 

dates had mean use values of equal to or less than 0.33 birds/30 min. Mean use by raptors was 

highest at NW-02 and NW-05, both of which include grasslands common to the NWTC (0.40 

birds/30 min; Figure 6a). Red-tailed hawks (4 observations) were the only raptor species 

observed at NW-02 (Table 4a). Raptors observed at NW-05 were American kestrel (3 

observations) and red-tailed hawk (1 observation; Table 4a). 
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2-6 October 2011 

Off-site locations 

A total of 95 birds from 13 species were observed in winter 2010 at off-site reference locations 

(Rocky Flats and Boulder County) during fixed-point count surveys (Table 2c). Overall avian 

mean use during winter 2010 was 1.76 birds/30 min (Table 2c).

Overall mean use by non-raptors in winter 2010 was 1.61 birds/30 min (range: 0–25 

individuals/survey). Among non-raptor species groups observed in winter 2010, mean use was 

highest for songbirds (1.15 birds/30 min; range: 0–12 individuals/survey; Table 3c). Species with 

the highest mean use for this species group were horned lark (0.48 birds/30 min; range: 0–12 

individuals/survey) and black-billed magpie (0.24 birds/30 min; range: 0–5 individuals/survey; 

Table 3c). All other songbird species had mean use values of equal to or less than 0.19 birds/30 

min. The waterfowl species group had the second highest non-raptor species group (0.46 

birds/30 min; range: 0–25 individuals/survey) which was comprised of a single observation of 25 

Canada geese (Table 3c). 

Non-raptor mean use was highest on February 2, 2010 (4.83 birds/30 min; Figure 3c). Mean use 

for non-raptors was highest at RF-01, which includes grasslands and a small portion of pine trees 

(4.00 birds/30 min; Figure 4c) and observations at this point included the flocks of Canada geese 

(25 individuals) and mountain bluebirds (6 individuals). Additional species observed at this site 

had only two individuals or less (Table 4g).

Overall mean use for raptors was 0.15 birds/30 min (range: 0–2 individuals/survey; Table 3c). 

Among the species groups observed in winter 2010, the raptor species group had the lowest 

mean use. Four raptor species were observed during winter: 2010: red-tailed hawk (0.07 birds/30 

min; range: 0–2 individuals/survey), great horned owl (0.04 birds/30 min; range: 0–1 

individuals/survey), northern harrier (0.02 birds/30 min; range 0–1 individuals/survey) and 

golden eagle (0.02 birds/30 min; range: 0–1 individuals/survey; Table 3c). 

Mean use by raptors was highest on January 22 and March 4 (0.33 birds/30 min; Figure 5c). 

Mean use by raptors was less than 0.20 birds/30 min for all other survey dates. Mean use by 

raptors was highest at point count location CB-01 and RF-01, which both include grasslands 

common to the NWTC and the vicinity, (0.33 birds/30 min; Figure 6c). Red-tailed hawks (3 

observations) were the only raptor species observed at CB-01 (Table 4g). Raptors observed at 

RF-01 were great horned owl (2 observations) and northern harrier (1 observation; Table 4g). 

Spring 2010 (March 26–June 17) 

NWTC points 

A total of 247 birds from 28 species were observed during spring 2010 at point locations within 

the NWTC (Table 2a). Overall avian mean use in spring 2010 was 3.43 birds/30 min (Table 2a). 

Overall mean use in spring 2010 by non-raptors was 3.17 birds/30 min (range: 0–12 

individuals/survey; Table 3a). Among non-raptor species groups observed in spring 2010, mean 
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2-7 October 2011 

use was highest for songbirds (3.01 birds/30 min; range: 0–12 individuals/survey; Table 3a). The 

songbirds with the highest mean use were the western meadowlark (1.17 birds/30 min; range: 0–

4 individuals/survey) and vesper sparrow (0.69 birds/30 min; range: 0–10 individuals/survey; 

Table 3a). All other songbird species had mean use equal to or less than 0.18 birds/30 min. The 

waterfowl species group had the second highest non-raptor species group (0.08 birds/30 min; 

range: 0–3 individuals/survey), comprised solely of the mallard (Table 3a). All remaining nonraptor species groups had mean use values of equal to or less than 0.04 birds/30 min. 

Non-raptor mean use was highest on May 5 (7.17 birds/30 min) and April 22, 2010 (6.33 

birds/30 min; Figure 3a). Mean use for non-raptors was highest at NW-01 (3.83 birds/30 min) 

and NW-06 (3.58 birds/30 min; Figure 4a). Both of these point locations include grasslands 

common to the NWTC. Observations at NW-01 included western meadowlark (12 observations) 

and barn swallow (10 observations; Table 4b). Observations at NW-06 included many 

observations of western meadowlark (15 observations) and vesper sparrow (11 observations; 

Table 4b).

Overall mean use in spring 2010 for raptors was 0.25 birds/30 min (range: 0–3 

individuals/survey; Table 3a). Among the species groups observed during spring 2010, the raptor 

species group had the second highest mean use. Raptors observed in this season were turkey 

vulture (0.10 birds/30 min; range: 0–3 individuals/survey), American kestrel (0.08 birds/30 min; 

range: 0–2 individuals/survey), red-tailed hawk (0.04 birds/30 min; range: 0–1 

individuals/survey), northern harrier (0.01 birds/30 min; range: 0–1 individuals/survey), and 

ferruginous hawk (0.01 birds/30 min; range: 0–1 individuals/survey). 

Mean use by raptors was highest on April 8 (0.67 birds/30 min; Figure 5a). Mean use by raptors 

was equal to or less than 0.50 birds/30 min for all other survey dates. Mean use by raptors was 

highest at point count location NW-02, which includes grasslands common to the NWTC (0.42 

birds/30 min; Figure 6a). Raptors observed at NW-02 included red-tailed hawk (2 observations), 

American kestrel (2 observations) and turkey vulture (1 observation; Table 4b). 

Off-site locations 

A total of 603 birds from 38 species were observed in spring 2010 at off-site reference locations 

(Rocky Flats and Boulder County) during fixed point count surveys (Table 2c). Overall avian 

mean use during spring 2010 was 8.38 birds/30 min (Table 2c).

Overall mean use in spring 2010 by non-raptors was 8.17 birds/30 min (range: 0–88 

individuals/survey). Among non-raptor species groups observed in spring 2010, mean use was 

highest for songbirds (7.25 birds/30 min; range: 0–88 individuals/survey; Table 3c). Songbirds 

with the highest mean use were red-winged blackbird (1.83 birds/30 min; range: 0–83 

individuals/survey) and western meadowlark (1.68 birds/30 min; range: 0–6 individuals/survey; 

Table 3c). All other songbird species had mean use values equal to or less than 0.96 birds/30 

min. The gulls and terns species group had the second highest mean use (0.56 birds/30 min; 0–
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2-8 October 2011 

40 individuals/survey) of the non-raptor species groups due to a single observation of 40 

Franklin’s gulls (Table 3c). All remaining non-raptor species groups had mean use values of 

equal to or less than 0.15 birds/30 min (Table 3c). 

Non-raptor mean use was highest on May 13 (19.67 birds/30 min; Figure 3c). Mean use by nonraptors was 15.67 birds/30 min or fewer for all other survey dates. Mean use for non-raptors was 

highest at point location RF-01 (15.25 birds/30 min; Figure 4c). The high mean use at point RF01 was greatly influenced by the 93 observations of red-winged blackbirds (Table 4h). 

Overall mean use in spring 2010 for raptors was 0.21 birds/30 min (range: 0–3 

individuals/survey). Among the species groups observed in spring 2010, the raptor species group 

had the third highest mean use. Raptors observed during this season were American kestrel (0.07 

birds/30 min; range: 0–1 individuals/survey), red-tailed hawk (0.04 birds/30 min; range: 0–2 

individuals/survey), Swainson’s hawk (0.04 birds/30 min; range: 0–1 individuals/survey), turkey 

vulture (0.03 birds/30 min; range: 0–2 individuals/survey), great horned owl (0.01 birds/30 min; 

range: 0–1 individuals/survey), and bald eagle (0.01 birds/30 min; range: 0–1 

individuals/survey). 

Mean use by raptors was highest on June 4 (1.17 birds/30 min; Figure 5c). Mean use by raptors 

was equal to or less than 0.50 birds/30 min for all other survey dates. Mean use by raptors was 

highest at point count locations RF-01 and RF-02, which both include grasslands common to the 

NWTC and the vicinity (0.33 birds/30 min; Figure 6c). Raptor species observed at point RF-01 

(Table 4h) included Swainson’s hawk (3 individuals) and a great horned owl (1 individual). 

Raptor species observed at point RF-02 (Table 4h) included American kestrel (2 individuals), 

red-tailed hawk (1 individual), and bald eagle (1 individual). 

Early Summer 2010 (June 23–July 8) 

NWTC points 

A total of 99 birds from 18 species were observed during early summer 2010 at point locations 

within the NWTC (Table 2a). Overall mean use in early summer 2010 was 5.82 birds/30 min 

(Table 2a). 

Overall mean use in early summer 2010 by non-raptors was 5.53 birds/30 min (range: 2–12 

individuals/survey). Among non-raptor species groups, mean use was highest for songbirds (5.35 

birds/30 min; range: 2–12 individuals/survey; Table 3a). Songbirds with the highest mean use 

were the vesper sparrow (1.94 birds/30 min; range: 0–7 individuals/survey) and western 

meadowlark (1.53 birds/30 min; range: 0–5 individuals/survey; Table 3a). All remaining nonraptor species groups had a mean use of equal to or less than 0.18 birds/30 min. 

Non-raptor mean use was highest on July 8 (7.80 birds/30 min; Figure 3a). Mean use for nonraptors was highest at NW-05, a grassland point location (7.50 birds/30 min; Figure 4a) and 
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2-9 October 2011 

observations at this point included vesper sparrow (9 individuals) and, western meadowlark (6 

individuals; Table 4c). 

Overall mean use in early summer 2010 for raptors was 0.29 birds/30 min (Table 3a; range: 0–2 

individuals/survey). The raptor species group had the second highest mean use among species 

groups. Raptors observed in early summer 2010 were the turkey vulture (0.18 birds/30 min; 

range: 0–1 individuals/survey) and red-tailed hawk (0.04 birds/30 min; range: 0–2 

individuals/survey). 

Mean use by raptors was highest on July 2 (0.50 birds/30 min; Figure 5a). Mean use by raptors 

was highest at point count location NW-02 and NW-04, both grassland point locations, (0.67 

birds/30 min; Figure 6a). Raptor species observed at NW-02 included red-tailed hawk (2 

individuals) and at NW-04 included turkey vulture (2 individuals; Table 4c). 

Off-site locations 

A total of 19 birds from 7 species were observed in early summer 2010 at off-site reference 

locations (Rocky Flats and Boulder County) during the fixed-point count surveys (Table 2c).

Overall avian mean use during early summer 2010 was 1.58 birds/30 min (Table 2c).

Overall mean use in early summer 2010 by non-raptors was 1.33 birds/30 min (range: 0–3 

individuals/survey) and the songbird species group had the highest mean use (1.25 birds/30 min; 

range: 0–3 individuals/survey; Table 3c). Songbirds with the highest mean use were western 

meadowlark (0.75 birds/30 min; range: 0–2 individuals/survey) and vesper sparrow (0.33 

birds/30 min; range: 0–2 individuals/survey; Table 3c). The only other non-raptor species group 

observed was the pigeon and dove species group with a mean use of 0.08 birds/30 min (range: 0–

1 individuals/survey; Table 3c). 

Non-raptor mean use was highest on July 2 (1.67 birds/30 min); Figure 3c). Mean use for nonraptors was highest at CB-01 and RF-02 (2.00 birds/30 min; Figure 4c). Observations at CB-01 

included western meadowlark (3 individuals) and common raven (1 individual). Observations at 

RF-03 included mourning dove (Table 4i).

Overall mean use in early summer 2010 for raptors was 0.25 birds/30 min (range: 0–2 

individuals/survey; Table 3c). The raptor species group had the second highest mean use among 

species groups. Raptors observed during this season were the American kestrel (0.17 birds/30 

min; range: 0-2 individuals/survey) and red-tailed hawk (0.08 birds/30 min; range: 0–1 

individuals/survey). 

Mean use by raptors was highest on July 2 (0.33 birds/30 min; Figure 5c). Mean use by raptors 

on all other days was equal to or less than 0.25 birds/30 min. Mean use by raptors was highest at 

point count location RF-01 (1.5 birds/30 min; Figure 6c). Two American kestrels and one redtailed hawk were observed at RF-01 (Table 4i). 
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2-10 October 2011 

Late Summer 2010 (July 16–August 27) 

NWTC points 

A total of 502 birds were observed during late summer 2010 at point locations within the 

NWTC. During the fixed-point count surveys, 501 birds from 25 species and 1 unknown bird 

(Table 2b). Overall avian mean use in late summer 2010 was 12.87 birds/20 min (Table 2b). 

Overall non-raptor mean use was 12.84 birds/20 min (range: 0-73 individuals/survey). Among 

non-raptor species groups, mean use was highest for songbirds (12.44 birds/20 min; range: 0–73 

individuals/survey; Table 3b). Species with the highest mean use for this species group were redwinged blackbird (2.54 birds/20 min; range: 0–51 individuals/survey) and western meadowlark 

(1.85 birds/20 min; range: 0–9 individuals/survey; Table 3b). All other songbird species had 

mean use equal to or less than 1.36 birds/20 min. The pigeons and doves species group had the 

second highest non-raptor species group (0.31 birds/20 min; range: 0–2 individuals/survey), 

largely due to the mourning dove (0.28 birds/20 min; range: 0–1 individuals/survey; Table 3b). 

All remaining non-raptor species groups had mean use values of equal to or less than 0.08 birds/ 

20 min (Table 3b). 

Non-raptor mean use was highest on July 20 (29.50 birds/20 min; Figure 3b). Mean use for nonraptors was highest at NW-02 (27.00 birds/20 min; Figure 4b) and observations at this point 

included red-winged blackbird (95 individuals) and Brewer’s blackbird (25 individuals; Table 

5d). Point count location NW-02 had more than two times the number of detected individuals 

than any other NWTC point count. 

Overall mean use in late summer 2010 for raptors was 0.03 birds/20 min (Table 3b). Among the 

species groups, the raptor species group had the lowest mean use. Only one raptor was observed 

during summer 2010, the red-tailed hawk (0.03 birds/20 min; range: 0–1 individuals/survey) 

observed at point count location NW-02 (Table 5d) on July 20. As a consequence, mean use by 

raptors was highest on July 20 (0.25 birds/20 min; Figure 5b). Mean use by raptors was highest 

at NW-02 (0.14 birds/20 min; Figure 6b), where the single red-tailed hawk was observed (Table 

4d). 

Off-site locations 

A total of 399 birds were observed in late summer 2010 at off-site reference locations (Rocky 

Flats and Boulder County). During the fixed-point count surveys, 398 birds from 22 species and 

1 bird that could not be identified to species (Table 2d). Overall avian mean use during late 

summer 2010 was 9.73 birds/20 min (Table 2d).

Overall mean use in late summer 2010 by non-raptors was 9.53 birds/20 min (range: 0–63 

individuals/survey). Among non-raptor species groups, mean use was highest for songbirds (9.27 

birds/20 min; range: 0–63 individuals/survey; Table 3d). Species with the highest mean use for 

this species group were horned lark (2.15 birds/20 min; range: 0–20 individuals/survey), western 
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2-11 October 2011 

meadowlark (1.66 birds/20 min; range: 0–7 individuals/survey) and grasshopper sparrow (1.61 

birds/20 min; range: 0–15 individuals/survey; Table 3d). All other songbird species had mean 

use equal to or less than 1.46 birds/20 min. The pigeons and doves species group had the second 

highest non-raptor species group (0.17 birds/20 min; range: 0–3 individuals/survey), comprised 

solely of the mourning dove (Table 3d). All remaining non-raptor species groups had mean use 

values of equal to or less than 0.07 birds/ 20 min; Table 3d). 

Non-raptor mean use was highest on July 20 (17.5 birds/20 min; Figure 3d). Mean use for nonraptors was highest at CB-03 (16.71 birds/20 min; Figure 4d) and observations at this point 

included European starling (60 individuals), western meadowlark (20 individuals), and 

grasshopper sparrow (15 individuals; Table 4j). European starlings were only observed off-site at 

CB-03. 

Overall mean use in late summer 2010 for raptors was 0.20 birds/20 min (range: 0–2 

individuals/survey; Table 3d). Among the species groups, the raptor species group had the lowest 

mean use. Only one raptor species was observed during late summer 2010, American kestrel, and 

was observed at both off-site locations, Rocky Flats and Boulder County (Table 4j). 

Mean use by raptors was highest on July 29, August 3, and August 19, 2010 (0.33 birds/20 min; 

Figure 5d). Mean use by raptors was 0.17 birds/20 min for all other survey dates. Mean use by 

raptors was highest at point count location CB-02 (1.00 birds/20 min; Figure 6d). A total of 

seven American kestrels were observed at point CB-02 (Table 4j). 

Fall 2010 (September 2–November 18) 

NWTC points 

A total of 205 birds were observed in fall 2010 at point locations within the NWTC. During the 

fixed-point count surveys, 195 birds from 26 identified species and 10 birds that could not be 

identified to species were observed (Table 2b). Overall mean bird use during fall 2010 was 3.25 

birds/20 min (Table 2b). 

Overall mean use in fall 2010 by non-raptors was 3.12 birds/20 min (range: 0–21 

individuals/survey; Table 3b). Among non-raptor species groups, mean use was highest for 

songbirds (2.65 birds/20 min; range: 0–21 individuals/survey; Table 3b). The non-raptors with 

the highest mean use were the western meadowlark (0.46 birds/20 min; range: 0–9 

individuals/survey), song sparrow (0.38 birds/20 min; range: 0–9 individuals/survey), and horned 

lark (0.32 birds/20 min; range: 0–5 individuals/survey; Table 3b). All other songbird species had 

mean use equal to or less than 0.24 birds/20 min. The pigeons/doves species group had the 

second highest non-raptor species group (0.22 birds/20 min; range: 0–3 individuals/survey), 

comprised solely of the mourning dove (Table 3b). The third highest species group was 

woodpeckers with a mean use of 0.14 birds/20 min (range: 0–4 individuals/survey) and was 

comprised of downy woodpecker (0.08 birds/20 min; range 0–4 individuals/survey) and northern 
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2-12 October 2011 

flicker (0.06 birds/20 min; range: 0–2 individuals/survey; Table 3b). All remaining non-raptor 

species groups had mean use values of equal to or less than 0.06 birds/20 min. 

Non-raptor mean use was highest on September 9 (9.8 birds/20 min) and September 2 (8.0 

birds/20 min; Figure 3b). Mean use for non-raptors was highest at NW-01 (4.92 birds/20 min) 

and NW-02 (4.83 birds/20 min; Figure 4b). Observations of non-raptors were not concentrated 

by any species at point NW-01 (Table 4e). However, at point NW-02, song sparrow (15 

individuals) and Brewer’s blackbird (10 individuals) contributed the most to the high mean use 

(Table 4e). 

Overall mean use in fall 2010 for raptors was 0.13 birds/20 min (range: 0–2 individuals/survey; 

Table 3b). Among the six species groups observed, the raptor species group had the fifth highest 

mean use. Raptors observed in this season were red-tailed hawk (0.06 birds/20 min; range: 0–2 

individuals/survey), American kestrel (0.05 birds/20 min; range: 0–1 individuals/survey), and 

sharp-shinned hawk (0.02 birds/20 min; range: 0–1 individuals/survey). 

Mean use by raptors was highest on October 28 (0.40 birds/20 min) and November 18 (0.33 

birds/20 min; Figure 5b). Mean use by raptors was equal to or less than 0.20 birds/20 min for all 

other fall 2010 survey dates. Mean use by raptors was highest at point count location NW-06 

(0.22 birds/20 min; Figure 6b). Raptors observed at NW-06 included two red-tailed hawks 

(Table 4e). 

Off-site locations 

A total of 335 birds were observed in fall 2010 at off-site reference locations (Rocky Flats and 

Boulder County). During the fixed-point count surveys, 326 birds from 25 species and 9 birds 

that could not be identified to species (Table 2d). Overall mean bird use during fall 2010 was 

4.86 birds/20 min and mean use for species ranged from 0.01 to 1.62 birds/20 min (Table 2d).

Overall mean use in fall 2010 by non-raptors was 4.64 birds/20 min (range: 0–53 

individuals/survey). Among non-raptor species groups, mean use was highest for songbirds (4.45 

birds/20 min; range: 0–53 individuals/survey; Table 3d). Songbirds with the highest mean use 

were western meadowlark (1.62 birds/20 min; range: 0–52 individuals/survey), song sparrow 

(0.57 birds/20 min; range: 0–12 individuals/survey), and vesper sparrow (0.49 birds/20 min; 

range: 0–25 individuals/survey; Table 3d). All other songbird species had mean use equal to or 

less than 0.29 birds/20 min. The pigeons and doves species group had the second highest mean 

use (0.12 birds/20 min; range: 0–3 individuals/survey) of the non-raptor species groups (Table 

3d). All remaining non-raptor species groups had mean use values of 0.04 birds/20 min or less 

(Table 3d). 

Non-raptor mean use was highest on September 9 and October 6 (12.0 birds/20 min; Figure 3d). 

Mean use by non-raptors was equal to or less than 10.5 birds/20 min for all other survey dates. 

Mean use for non-raptors was highest at point locations CB-02 (6.67 birds/20 min) and CB-03 
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2-13 October 2011 

(5.75 birds/20 min; Figure 4d). The high mean use at point CB-02 was greatly influenced by the 

58 observations of western meadowlark (Table 4k). However, at point CB-03 song sparrow (13 

individuals), western meadowlark (11 individuals), and lark bunting (12 individuals) contributed 

the most to the high mean use (Table 4k). 

Overall mean use in fall 2010 for raptors was 0.22 birds/20 min (range: 0-3 individuals/survey). 

Among the five species groups, the raptor species group had the second highest mean use. 

Raptors observed during this season were American kestrel (0.12 birds/20 min; range: 0–3 

individuals/survey), turkey vulture (0.07 birds/20 min; 0-3 individuals/survey) and red-tailed 

hawk (0.03 birds/20 min; range 0-1 individuals/survey). 

Mean use by raptors was highest on September 16 (0.83 birds/20 min) and September 2 (0.67 

birds/20 min; Figure 5d). Mean use by raptors was equal to or less than 0.33 birds/20 min for all 

other survey dates. Mean use by raptors was highest at point count locations CB-02 and CB-03 

(0.50 birds/20 min; Figure 6d). Raptor species observed at point CB-02 (Table 4k) included 

American kestrel (5 individuals) and a red-tailed hawk (1 individual). Raptor species observed at 

point CB-03 included turkey vulture (4 individuals) and American kestrel (2 individuals; Table 

4k). 

Winter 2010-2011 (December 7–February 14) 

NWTC points 

A total of 35 birds were observed in winter 2010–2011 within the point count locations at 

NWTC during the winter survey season. This included 8 species and 1 bird that could not be 

identified to species (Table 2b). Overall mean bird use within the NWTC was 1.25 birds/20 min 

and mean use for species ranged from 0.04 to 0.68 birds/20 min (Table 2b). 

Overall mean use by non-raptors was 1.18 birds/20 min (range: 0–10 individuals/survey). 

Among non-raptor species groups, mean use was highest for songbirds (1.14 birds/20 min; 

range: 0–10 individuals/survey; Table 3b). Songbirds with the highest mean use were the blackbilled magpie (0.68 birds/20 min; range: 0–9 individuals/survey) and common raven (0.25 

birds/20 min; range: 0–2 individuals/survey; Table 3b). All remaining non-raptor species groups 

had a mean use of equal to or less than 0.11 birds/20 min. 

Non-raptor mean use was highest on December 7 (2.4 birds/20 min; Figure 3a). Mean use for 

non-raptors was highest at NW-06 (3.20 birds/20 min; Figure 4b) and observations at this point 

included black-billed magpie (14 individuals; Table 4f). Point count location NW-06 had more 

than two times the number of detected individuals than any other NWTC point count during this 

season. 

Overall mean use in winter 2010–2011 for raptors was 0.08 birds/20 min (range: 0–1 

individuals/survey; Table 3b). The raptor species group had the second highest mean use among 

species groups. Raptors observed in winter 2010–2011 were the red-tailed hawk (0.04 birds/20 
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min; range: 0–1 individuals/survey) and American kestrel (0.04 birds/20 min; range: 0–1 

individuals/survey; Table 3b). 

Mean use by raptors was highest on December 7 (0.20 birds/20 min; Figure 5b). Raptors were 

also observed on January 23 with a mean use of 0.17 birds/20 min (Figure 5b. No raptors were 

observed on other survey dates on site. Mean use by raptors was highest at point count location 

NW-04 (0.40 birds/20 min; Figure 6b). Raptor species observed at NW-04 included an American 

kestrel (1 individual) and a red-tailed hawk (1 individual; Table 4f). 

Off-site locations 

A total of 33 birds were observed in winter 2010–2011 at offsite point count locations (Rocky 

Flats and Boulder County). This included 24 birds from 7 species and 9 birds that could not be 

identified to species (Table 2d). Overall mean bird use during winter was 1.00 bird/20 min and 

mean use for species ranged from 0.03 to 0.27 birds/20 min (Table 2d).

Overall mean use by non-raptors was 0.82 birds/20 min (range: 0–8 individuals/survey) and 

songbirds were the only non-raptor species group detected during winter 2010–2011 at off-site 

locations (Table 3d). Songbirds with the highest mean use were unidentified songbirds (0.27 

birds/20 min; range: 0–8 individuals/survey), American tree sparrow (0.18 birds/20 min; range 

0–5 individuals/survey), common raven (0.15 birds/20 min; range: 0–2 individuals/survey), and 

horned lark (0.12 birds/20 min; range: 0–2 individuals/survey; Table 3d). 

Non-raptor mean use was highest on December 29, 2010 (1.8 birds/20 min) and January 12, 

2011 (1.5 birds/20 min; Figure 3d). Mean use by non-raptors was equal to or less than 0.67 

birds/20 min for all other survey dates. Mean use for non-raptors was highest at RF-03 (3.60 

birds/20 min; Figure 4d) and observations at this point included American tree sparrow (5 

individuals) and several unidentified songbirds (8 individuals; Table 4l).

Overall mean use in winter 2010–2011 for raptors was 0.18 birds/20 min (range: 0–2 

individuals/survey; Table 3d). The raptor species group had the second highest mean use among 

species groups. Raptors observed in winter 2010–2011 at off-site locations were the red-tailed 

hawk (0.09 birds/20 min; range: 0–2 individuals/survey) and northern harrier (0.09 birds/20 min; 

range: 0–1 individuals/survey). 

Mean use by raptors was highest on December 7 (0.50 birds/20 min; Figure 5b). Mean use by 

raptors was equal to or less than 0.25 birds/20 min for all other survey dates. Mean use by raptors 

was highest at point count location RF-01 (0.33 birds/20 min; Figure 6d). Two red-tailed hawks 

were observed at RF-01 (Table 4l). 

2.5.2 Flight Height and Encounter Rate, 2010–2011 survey data 

Flight heights reported here are only for birds recorded at NWTC point count locations and the 

calculated encounter rates are for RSAs for the three large turbines (1.5 MW, 2.3 MW, and 3.0 
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MW) observed during 30-minute point count surveys from January 13 to July 8, 2010, and 

during 20-minute point count surveys from July 16, 2010, to February 14, 2011. 

1.5-MW Turbine 

Winter 2010 

Of non-raptor species observed flying in winter 2010, none were observed above, 33.3 percent 

flew within, and 66.7.0 percent flew below the height of the 1.5-MW RSA (Table 5a). Only one 

species, the common raven, was observed flying within the 1.5-MW RSA (0.05 birds flying at 

1.5-MW RSA height/30 min; Table 6a). No raptor species were observed flying within the height 

of the 1.5-MW RSA. All other species were observed flying below the RSA.

Spring 2010 

Of non-raptor species observed flying in spring 2010, none were observed above, 1.8 percent 

flew within, and 98.2 percent flew below the height of the 1.5-MW RSA (Table 5a). Of raptor 

species observed flying, none were observed above, 41.7 percent flew within, and 58.3 percent 

flew below the height of the 1.5-MW RSA. Four species (turkey vulture, red-tailed hawk, 

common raven, and ferruginous hawk) were observed flying at 1.5-MW RSA height. Turkey 

vulture had at the highest encounter rate at 0.04 birds flying at 1.5-MW RSA height/30 min and 

red-tailed hawk, common raven, and ferruginous hawk had an encounter rate of 0.01 birds flying 

at 1.5-MW RSA height/30 min (Table 6b). All other species were observed flying below the 1.5-

MW RSA. 

Early Summer 2010 

Of non-raptor species observed flying, 100 percent flew below the height of the 1.5-MW RSA 

(Table 5a). Of raptor species observed flying, 100 percent flew below the height of the 1.5-MW 

RSA. 

Late Summer 2010 

Of non-raptor species observed flying, 1.0 percent flew within and 99.0 percent flew below the 

height of the 1.5-MW RSA (Table 5b). No raptor species were observed flying during summer 

2010. Two species, common raven and grasshopper sparrow, were observed flying within the 

1.5-MW RSA and had calculated encounter rates of 0.05 and 0.03 birds flying within the 1.5-

MW RSA/20 min, respectively (Table 6d). All other species were observed flying below the 1.5-

MW RSA.

Fall 2010 

Of non-raptor species observed flying, 3.6 percent flew within and 96.4 percent flew below the 

height of the 1.5-MW RSA (Table 5b). Of raptor species observed flying, 16.7 percent flew 

within and 83.3 percent flew below the height of the 1.5-MW RSA. A flock of sandhill cranes 

were observed flying at RSA height with an encounter rate of 0.06 birds flying at the 1.5-MW 

RSA height/20 min, and red-tailed hawks had an encounter rate of 0.01 birds flying at the 1.5-
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MW RSA height/20 min (Table 6e). All other species were observed flying below the 1.5-MW 

RSA. 

Winter 2010–2011 

Of non-raptor species observed flying, 3.6 percent flew within and 96.4 percent flew below the 

height of the 1.5-MW RSA (Table 5b). Of raptor species observed flying, none were observed 

above or at the height of the RSA; therefore, 100 percent flew below the height of the RSA. Only 

one species, common raven, was observed flying within the RSA (0.04 birds flying within the 

RSA/20 min; Table 6f). All other species were observed flying below the RSA.

2.3-MW Turbine 

Winter 2010 

Of non-raptor species observed flying, 33.3 percent flew at the height of the RSA and 66.7 

percent flew below the height of the 2.3-MW RSA (Table 5c). Only the common raven was 

observed flying at the height of the 2.3-MW RSA and had an encounter rate of 0.05 birds flying 

at 2.3-MW RSA height/30 min (Table 6g). All other species were observed flying below the 2.3-

MW RSA. Of raptor species observed flying, 100 percent flew below the height of the 2.3-MW 

RSA. No raptors were observed flying at 2.3-MW RSA height; therefore, no encounter rates 

were calculated.

Spring 2010 

Of non-raptor species observed flying, 14.0 percent flew within and 86.0 percent flew below the 

height of the 2.3-MW RSA (Table 5c). Of raptor species observed flying, 66.7 percent flew 

within and 33.3 percent flew below the height of the 2.3-MW RSA. Five species (barn swallow, 

turkey vulture, common raven, red-tailed hawk, and ferruginous hawk) were observed flying at 

2.3-MW RSA height. Barn swallow and turkey vulture had the highest encounter rates at 0.10 

and 0.09 birds flying at 2.3-MW RSA height/30 min, respectively (Table 6h). Red-tailed hawk, 

common raven, and ferruginous hawk all had encounter rates of 0.01 birds flying at 2.3-MW 

RSA height/30 min (Table 6h). All other species were observed flying below the 2.3-MW RSA.

Early Summer 2010 

Of non-raptor species observed flying, 100 percent flew below the height of the 2.3-MW RSA 

(Table 5c). Of raptor species observed flying, 100 percent flew below the height of the 2.3-MW 

RSA. No species were observed flying at 2.3-MW RSA height; therefore, no encounter rates 

were calculated.

Late Summer 2010 

Of non-raptor species observed flying, 2.0 percent flew within and 98.0 percent flew below the 

height of the 2.3-MW RSA (Table 5d). No raptor species were observed flying during summer 

2010. Three species were observed flying at 2.3-MW RSA height: horned lark (0.08 birds flying 
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2-17 October 2011 

at 2.3-MW RSA height/20 min), common raven (0.05 birds flying at 2.3-MW RSA height/20 

min), and grasshopper sparrow (0.03 birds flying at 2.3-MW RSA height/20 min; Table 6j). 

Fall 2010 

Of non-raptor species observed flying, 9.0 percent flew within and 91.0 percent flew below the 

height of the 2.3-MW RSA (Table 5d). Of raptor species observed flying, 33.3 percent at and 

66.7 flew below the height of the 2.3-MW RSA. Five species were observed flying at 2.3-MW 

RSA height: sandhill crane (0.06 birds flying at 2.3-MW RSA height/20 min), song sparrow 

(0.06 birds flying at RSA 2.3-MW height/20 min), mourning dove (0.03 birds flying at 2.3-MW 

RSA height/20 min), American kestrel (0.02 birds flying at 2.3-MW RSA height/20 min), and 

grasshopper sparrow (0.01 birds flying at 2.3-MW RSA height/20 min; Table 6k) 

Winter 2010–2011 

Of non-raptor species observed flying, 7.1 percent flew within and 92.9 percent flew below the 

height of the 2.3-MW RSA (Table 5d). Of raptor species observed flying100 percent flew below 

the height of the RSA. Two species, common raven and black-billed magpie, were observed 

flying at 2.3-MW RSA height (0.04 birds flying within the 2.3-MW RSA/20 min; Table 6l). All 

other species were observed flying below the 2.3-MW RSA.

3.0-MW Turbine 

Winter 2010 

Of non-raptor species observed flying, 33.3 percent flew within and 66.7 percent flew below the 

height of the 3.0-MW RSA (Table 5e). Of raptor species observed flying, 100 percent flew 

below the height of the 3.0-MW RSA. Only one species, common raven, was observed flying 

within the 3.0-MW RSA (0.05 birds flying within the 3.0-MW RSA/30 min; Table 6m). All 

other species were observed flying below the 3.0-MW RSA.

Spring 2010 

Of non-raptor species observed flying, 1.8 percent flew within and 98.2 percent flew below the 

height of the 3.0-MW RSA (Table 5e). Of raptor species observed flying, 41.7 percent flew 

within and 58.3 percent flew below the height of the 3.0-MW RSA. Four species (turkey vulture, 

red-tailed hawk, common raven, and ferruginous hawk) were observed flying at 3.0-MW RSA 

height. Turkey vulture at the highest encounter rate at 0.04 birds flying at 3.0-MW RSA 

height/30 min (Table 6n). Red-tailed hawk, common raven, and ferruginous hawk had encounter 

rates of 0.01 birds flying at 3.0-MW RSA height/30 min (Table 6n). All other species were 

observed flying below the RSA.

Early Summer 2010 

Of non-raptor species observed flying, 100 percent flew below the height of the 3.0-MW RSA 

(Table 5e). Of raptor species observed flying, 100 percent flew below the height of the 3.0-MW 
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RSA. As all other species were observed flying below the 3.0-MW RSA; thus, no encounter rates 

were calculated. 

Late Summer 2010 

Of non-raptor species observed flying, 2.0 percent flew within and 98.0 percent flew below the 

height of the 3.0-MW RSA (Table 5f). No raptor species were observed flying during summer 

2010. Three species were observed flying at 3.0-MW RSA height: horned lark (0.08 birds flying 

at 3.0-MW RSA height/20 min), common raven (0.05 birds flying at 3.0-MW RSA height/20 

min), and grasshopper sparrow (0.03 birds flying at 3.0-MW RSA height/20 min; Table 6p). All 

other species were observed flying below the 3.0-MW RSA. 

Fall 2010 

Of non-raptor species observed flying, 8.1 percent flew within and 91.9 percent flew below the 

height of the 3.0-MW RSA (Table 5f). Of raptor species observed flying, 16.7 percent flew at 

and 83.3 flew below the height of the 3.0-MW RSA. Four species were observed flying at 3.0 

MW RSA height: sandhill crane (0.06 birds flying at 3.0-MW RSA height/20 min), song sparrow 

(0.05 birds flying at 3.0-MW RSA height/20 min), mourning dove (0.03 birds flying at 3.0-MW 

RSA height/20 min), and red-tailed hawk (0.01 birds flying at 3.0-MW RSA height/20 min; 

Table 6q). All other species were observed flying below the 3.0-MW RSA.

Winter 2010–2011 

Of non-raptor species observed flying, 3.6 percent flew within and 96.4 percent flew below the 

height of the 3.0-MW RSA (Table 5f). Of raptor species observed flying, 100 percent flew below 

the height of the 3.0-MW RSA. Only one species, common raven, was observed flying within 

the 3.0-MW RSA (0.04 birds flying within the 3.0-MW RSA/20 min; Table 6r). All other species 

were observed flying below the 3.0-MW RSA. 

2.5.3 Incidental Observations, 2010–2011 Data 

Incidental observations of birds were documented at the NWTC and off-site locations for 

individuals observed outside of point count survey periods during January 2010 to February 

2011 (see Section 2.3.2). 

Winter 2010 

NWTC and off-site locations 

Biologists documented 10 identified species and a total of 98 individuals as incidental 

observations (Table 7a). All raptor species observed as incidentals were also recorded during 

point count surveys – red-tailed hawk (8 incidental observations), American kestrel, (1 incidental 

observation), and rough-legged hawk (1 incidental observation). Of incidentals observed during 

winter 2010, 4 species (25–33 individuals) were observed flying at the height of one or more of 

the large turbine RSAs. 
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Spring 2010 

NWTC and off-site locations 

No incidental species were recorded.

Early Summer 2010 

NWTC and off-site locations 

No incidental species were recorded. 

Late Summer 2010 

NWTC 

Biologists documented 20 identified species and a total of 204 individuals as incidental 

observations (Table 7b). Red-tailed hawk (3 incidental observations) was recorded both as an 

incidental observation and during the point count surveys. Biologists also documented 2 

incidental raptor species – ferruginous hawk (1 observation) and Swainson’s hawk (1 

observation) – that were not detected during summer point count surveys. Of incidental species 

observed on site during late summer, only 2 species were observed at RSA height for the large 

turbines. A single vesper sparrow was observed at RSA height for the 2.3-MW and 3.0-MW 

turbines and a single red-tailed hawk was observed at RSA height for all of the large turbines. 

Off-site 

Biologists documented 14 identified species and a total of 38 individuals as incidental 

observations (Tables 7c-d). Biologists observed the American kestrel both as incidentals and 

during the point count surveys. Biologists also documented 2 incidental raptor species – redtailed hawk (1 observation) and Swainson’s hawk (4 observations) – that were not detected 

during summer point count surveys. 

Fall 2010 

NWTC 

Biologists documented 12 identified species and a total of 212 individuals as incidental 

observations (Table 7b). One raptor species – northern harrier (1 observation) – was reported as 

an incidental but was not detected during fall point count surveys. Of incidental species observed 

on site during fall, five unknown raptor species were recorded at RSA height for the 2.3-MW 

turbine. 

Off-site 

Biologists documented 9 identified species and a total of 39 individuals as incidental 

observations (Tables 7c-d). American kestrels were observed both as incidentals and during the 

point count surveys. Biologists also documented two incidental raptor species – golden eagle (1 

observation) and northern harrier (4 observations) – that were not detected during fall point count 

surveys. 
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Winter 2010–2011 

NWTC 

Biologists documented 6 identified species and a total of 43 individuals as incidental 

observations (Table 7b). American kestrel (1 incidental observation) was recorded as an 

incidental and during the point count surveys. Of incidental species observed on site during 

winter, only 1 species, the common raven (1 individual), was observed at RSA height for the 

three large turbines. 

Off-site 

Biologists documented 13 identified species and a total of 196 individuals as incidental 

observations (Tables 7c-d). Red-tailed hawks and northern harriers were observed both as 

incidentals and during the point count surveys. Biologists also documented 3 incidental raptor 

species – golden eagle (1 observation), prairie falcon (1 observation), and great horned owl (2 

observations) – that were not detected during winter point count surveys. 

2.5.4 Protected Species, 2010-2011 Data 

During all point count surveys conducted during 2010–2011, no federal threatened or 

endangered species were observed during avian point count surveys or as incidental observations 

at the NWTC or off-site locations. No state threatened or endangered species were observed 

during 2010–2011 avian point count surveys or as an incidental observation at the NWTC or offsite locations. 

Two species of concern for Colorado, ferruginous hawks and sandhill cranes, were observed 

incidentally to or during point count surveys. Ferruginous hawks were observed during spring 

surveys at the NWTC at point location NW-01 (May 5) and were also recorded as an incidental 

observation during summer 2010 (Table 7b). Ferruginous hawks had a mean use of 0.01 birds/30 

min (Table 3a) and an encounter rate of 0.01 birds flying at RSA height/30 min for all three large 

turbines (Tables 6b, h, n). A single flock of 4 sandhill cranes was observed during fall point 

count surveys at NWTC point count location NW-06 (Table 4e). This group of sandhill cranes 

was only observed flying and had a mean use 0.06 birds/20 min. Despite differences in RSAs, 

the encounter rate was the same for sandhill cranes (0.06 birds flying at RSA height/20min) at 

each of the three large turbines. 

Bald and golden eagles, federally protected by the BGEPA, were observed on Rocky Flats 

during and incidental to point count surveys. A bald eagle was observed at RF-02 on May 5, 

2010, and had a mean use of 0.01 birds/30 min (Table 2c). A golden eagle was observed during 

point count surveys on February 17, 2010, at RF-02 and had a mean use of 0.02 birds/30 min 

(Table 2c). Golden eagles were also observed incidental to point count surveys near point count 

location RF-03 on November 4 and December 7 (Table 7d). No eagles were observed on the 

NWTC site; thus, no encounter rates were calculated. 
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2.5.5 Comparison to Historical Data 

This section compares 2010–2011 results with Schmidt et al. (2003) based on avian abundance. 

Tables 8a-l present non-raptors seen at the NWTC and at off-site points during 2010–2011 

surveys for each season and as an annual summary. Comparisons between Schmidt et al. (2003) 

and the 2010–2011 avian use surveys could not be made for grassland bird use within the NWTC 

at locations with and without facilities. During the 2001–2002 study, point location NW-06 was 

utilized as a control location within the NWTC and did not have wind energy facilities. This 

point location is now developed as Site 4.4, site of the 3.0-MW Siemens wind turbine. Since it 

was not possible to compare grasslands within the NWTC with and without facilities, 

comparisons have been made between NW-06 and the other on-site grassland points (NW-02, 

NW-03, NW-04, NW-05) to show changes over time. However, comparisons can be made 

between grassland bird use at the off-site reference locations (Boulder County and Rocky Flats) 

and the NWTC during the 2001–2002 and 2010–2011 point count surveys and provides 

information regarding avian use at sites with and without facilities. 

Birds in Grasslands 

Small Birds 

NWTC grasslands 

Schmidt et al. (2003) reported western meadowlark, vesper sparrow, European starling, 

mourning dove, and black-billed magpies as the most abundant species. Similarly, western 

meadowlark, red-winged blackbird, vesper sparrow, horned lark, and Brewer’s blackbird were 

the most abundant species during the 2010–2011 surveys. Species diversity and composition 

varied between survey periods, 15 species were observed during 2001–2002 surveys and 27 

species were seen during 2010–2011 surveys. 

Off-site grasslands 

Schmidt et al. (2003) reported vesper sparrow, western meadowlark, horned lark, cliff swallow, 

and common raven as the most abundant species. Similarly, western meadowlark, horned lark, 

vesper sparrow, red-winged blackbird, and grasshopper sparrow were the most abundant species 

during the 2010–2011 surveys. Species diversity and composition varied between survey 

periods, 29 species were observed during 2001–2002 surveys and 36 species were seen during 

2010–2011 surveys. 

Raptors and Large Birds 

NWTC grasslands 

Schmidt et al. (2003) reported American kestrel, red-tailed hawk, and northern harrier as the 

most abundant raptors or large birds. During 2010–2011 surveys, red-tailed hawk, American 

kestrel, and mallard were the most abundant raptors or large birds. Species diversity and 

composition varied between survey periods, 12 species were observed during 2001–2002 surveys 

and 6 species were seen during 2010–2011 surveys. Sandhill cranes were observed at NWTC 

grassland points during 2010–2011 surveys but not during 2001–2002 surveys. Additional large 
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birds seen during the 2001–2002 surveys include great blue heron, double crested cormorant, 

golden eagle, rough-legged hawk, ferruginous hawk, prairie falcon, and peregrine falcon. 

Off-site grasslands 

Schmidt et al. (2003) reported American kestrel, red-tailed hawk, and northern harrier as the 

most abundant raptors or large birds. During 2010–2011 surveys, American kestrel, red-tailed 

hawk, and turkey vulture were the most abundant raptors or large birds. Species diversity and 

composition varied between survey periods, 12 species were observed during 2001–2002 surveys 

and 9 species were seen during 2010–2011 surveys. Ferruginous hawk, rough-legged hawk, 

double-crested cormorant, great blue heron, and prairie falcon were observed at the off-site 

grassland points during 2001–2002 surveys but not during 2010–2011 surveys. Additional large 

birds seen during the 2010–2011 surveys include mallard and greater scaup. 

Birds in Pine Forest 

Schmidt et al. (2003) compared pine plots at NW-01 to two Boulder County point count 

locations. However, during 2010–2011 surveys, there were no pine plots available for 

comparison to NW-01 at the surveyed Boulder County point count locations (CB-01, CB-02, and 

CB-03). RF-01 was the only reference site with a grouping of pine trees but was not a site 

originally considered a “pine plot” by Schmidt et al. (2003). Therefore, for pine plot comparison 

the NWTC pine plot was NW-01 and the off-site pine plot was RF-01. 

Small Birds 

NWTC pine plot 

Schmidt et al. (2003) reported chipping sparrow, western meadowlark, mountain bluebird, blackbilled magpie, and vesper sparrow as the most abundant species. During 2010–2011 surveys, 

western meadowlark, vesper sparrow, barn swallow, American robin, and grasshopper sparrow 

were the most abundant species. Species diversity and composition varied between survey 

periods, 21 species were observed during 2001–2002 surveys and 29 species were seen during 

2010–2011 surveys. 

Off-site pine plot 

Schmidt et al. (2003) reported chipping sparrow, western meadowlark, vesper sparrow, tree 

swallow, and black billed magpie as the most abundant species. During 2010–2011 surveys, redwinged blackbird, western meadowlark, vesper sparrow, horned lark, and black-billed magpie 

were the most abundant species. Species diversity and composition varied between survey 

periods, 10 species were observed during 2001–2002 surveys and 26 species were seen during 

2010–2011 surveys. 
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Raptors and Large Birds 

NWTC pine plot 

Schmidt et al. (2003) reported American kestrel, red-tailed hawk, and northern harrier as the 

most abundant raptors and large birds. During 2010–2011 surveys, turkey vulture, American 

kestrel and red-tailed hawk were the most abundant raptors and large birds. Although species 

composition varied, 5 species were seen during both survey time periods. Northern harriers, a 

double-crested cormorant, and a golden eagle were observed during 2001–2002 surveys but not 

during 2010–2011 surveys. Turkey vultures, a ferruginous hawk, and sharp-shinned hawk were 

observed during 2010–2011 surveys but not during 2001–2002 surveys. 

Off-site pine plot 

Schmidt et al. (2003) reported American kestrel, red-tailed hawk, and northern harrier as the 

most abundant raptors and large birds. During 2010–2011 surveys, Canada goose, red-tailed 

hawk, and Swainson’s hawk were the most abundant raptors and large birds. Species diversity 

and composition varied between survey periods, 3 species were observed during 2001–2002 

surveys and five species were seen during 2010–2011 surveys. American kestrels were observed 

at the pine plot during 2001–2002 surveys but not during 2010–2011 surveys. Additional large 

birds seen during the 2010–2011 surveys include Canada goose, Swainson’s hawk, great blue 

heron, and mallard. 

2.6 DISCUSSION AND RECOMMENDATIONS 

The bird community of the NWTC was comprised primarily of grassland birds and 

forest/shrubland birds. However, the number of species and individuals present varied based on 

season. Birds with the overall highest mean use were western meadowlark, red-winged 

blackbird, horned lark, and grasshopper sparrow. These species are associated with the open 

grasslands found throughout the NWTC. 

As the results of the avian surveys conducted in 2001–2002 and 2010–2011 indicate, bird 

diversity, abundance, and frequency of site use vary seasonally and yearly. These fluctuations 

can be attributed to many changes (e.g., food resources, breeding, migration, and available 

habitat). One factor that commonly changes bird community composition is precipitation. 

According to the Palmer Drought Suitability Index, 2001–2002 surveys were conducted during 

near normal precipitation (2001) and moderate drought (2002) conditions in the Colorado Platte 

Drainage Basin region (Figure 7; NCDC 2010). In contrast, 2010–2011 precipitation conditions 

were above normal for the Colorado Platte Drainage Basin region with conditions ranging from 

unusually wet to extremely wet (Figure 7). Changes in precipitation likely alter the diversity, 

distribution, and number of individuals of the avian community observed within the NWTC and 

on off-site locations and can compound influences of season and migration patterns within the 

NWTC and resulting encounter rates. Seasonal and annual fluctuations in avian use of the 

NWTC are expected. It is therefore important to note when considering the results that multiple 

factors influence the probability of a species to have negative interactions with turbines, met 
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towers, or guy wires, including the number of individuals at the site and the frequency that the 

species flies at RSA height. Additionally, the relationship between avian use and postconstruction mortality is not yet completely well-defined (NWCC 2010). Conclusions discussed 

below were based upon available data. 

2.6.1 Non-Raptor Use and Encounter Rate 

Songbirds consistently had the highest mean use out of all species groups during surveys at the 

NWTC and off site. Songbird species which contributed most to this overall value varied by 

season and had higher values of mean use during the summer breeding season. Western 

meadowlark, grasshopper sparrow, and horned lark had the highest mean use on site relative to 

other species, especially during the summer (Tables 3a-b). Horned lark, western meadowlark, 

and grasshopper sparrow are grassland birds and were observed at all point count locations. The 

grassland habitat of the NWTC provides favorable conditions for these species. Additionally, 

red-winged blackbirds contributed high mean use values on the NWTC during the summer (2.54 

birds/20 min; Table 2b). Of the 99 individual red-winged blackbirds observed during point count 

surveys, 95 were detected at NW-02 (Table 4d). As previously mentioned, precipitation 

conditions were above normal during summer point counts and high mean use values of redwinged blackbirds can be attributed to the use of a small pond south of NW-02 near the NWTC 

boundary. Despite high mean use by songbirds within the NWTC, all non-raptors had encounter 

rates of 0.10 birds flying within the RSA/20 min or 30 min or less (Tables 6a-r). 

Within the NWTC, western meadowlark, red-winged blackbird, horned lark, and grasshopper 

sparrow were among the most numerous non-raptors observed; population-level impacts appear 

to be minimal because a low proportion of individuals were observed flying at RSA height. Of 

these species, only horned larks and grasshopper sparrow were observed flying at RSA height 

(0.08 and 0.03 birds flying at RSA height/20 min, respectively) despite high mean use (Tables 

6a-r). Horned lark is one of the most common species with fatalities at wind projects in the 

Columbia Plateau Ecoregion in Washington and Oregon (Johnson and Erickson 2010). Horned 

larks are susceptible to collision during the breeding season because male horned larks fly to 

heights of 80 m to 250 m for breeding displays (Pickwell 1931). 

Other non-raptor species observed flying at RSA height were barn swallow, song sparrow, 

common raven, black-billed magpie, and mourning dove. Barn swallows had a low mean use 

value (0.18 birds/20 min) and low encounter rate (0.10 birds flying at RSA height/20 min), 

therefore it is unlikely the NWTC development will affect the regional population of barn 

swallows. Fatalities of songs sparrows have been documented at wind energy facilities 

(Thelander et al. 2003, Erickson et al. 2007a, Johnson and Erickson 2010). However, low mean 

use (0.38 birds/20 min) and low encounter rates (0.06 birds flying at RSA height/20 min) 

indicate that any song sparrow fatalities, should they occur, are likely to be few. Common raven 

were observed flying at RSA heights during many seasons for all three large turbines with the 

highest encounter rate calculated being 0.05 birds flying at RSA height/20 min Tables 6a-r). 
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Mean use for common raven on site was 0.25 birds/20 min or less (Tables 2a-b). Although 

common ravens have been documented as fatalities at wind energy facilities, low mean use and 

encounter rates across seasons suggest that it is unlikely that there is great potential for turbinerelated impacts to the common raven at NWTC (Orloff and Flannery 1992, Anderson et al. 

2005). Encounter rates observed for all non-raptors was low at 0.10 birds flying at RSA 

height/20 min or less (Tables 6a-r); therefore, should any fatalities occur population-level 

impacts would appear to be minimal because a low proportion of individuals were observed 

flying at RSA height. 

Incidentally observed species were also observed flying at RSA height; however, encounter rates 

cannot be calculated for these species because they were not observed during a timed survey 

period. Non-raptors observed in the RSA incidentally that were not discussed above with 

encounter rates include Canada goose and vesper sparrow. A flock of 20 Canada geese was 

observed flying at RSA height for all three turbines during winter 2010. In winter 2010–2011, a 

smaller flock of 9 Canada geese was observed flying above the RSA height for all three turbines. 

The number of waterfowl and other wading birds found at wind farms and communications 

towers is low, suggesting that these taxa avoid these structures (Crawford and Engstrom 2001, 

Erickson et al. 2004, Anderson et al. 2005, Jain et al. 2007). Few fatalities of Canada geese have 

been found as fatalities under wind turbines (Johnson and Erickson 2010); therefore, it is 

unlikely that Canada geese will be greatly affected by the development of the site. A single 

vesper sparrow of the 10 recorded incidentally during late summer 2010 was observed at RSA 

height for the 2.3-MW and the 3.0-MW turbines. Few vesper sparrows have been found as 

fatalities at wind turbines (Young et al. 2003, Johnson and Erickson 2010). Therefore, should 

any fatalities occur, population-level impacts would appear to be minimal because a low 

proportion of individuals were observed flying at RSA height.

2.6.2 Raptor Use and Encounter Rate 

High raptor use (greater than 2.0 birds/20 min) has been associated with higher raptor mortality 

rates (0.35 raptors/MW/yr) at wind energy facilities (Erickson 2007). Conversely, raptor 

mortality appears to be low (less than 0.15 raptors/MW/yr) when raptor use is low, as defined by 

Erickson (2007) as less than 1.0 birds/20 min, which is the case for raptor use at the NWTC 

during all seasons. According to raptor use as defined by Erickson (2007), raptor mean use at the 

NWTC was low (0.08 birds/20 min and 0.23 birds/30 min) when taking all survey seasons into 

account (Tables 3a-b). 

Mean use by raptors was highest at point count location NW-04 during fall 2010 (0.40 birds/20 

min; Figure 6b). This location has several large met towers that could serve as perches for 

raptors in addition to open grassland habitats for foraging. However, this point received 

moderate usage when comparing mean use at all points within the NWTC and at offsite points 

over the surveyed seasons (Figures 6a-d). Highest mean use occurred at point count location CB02 (1.00 birds/20 min) during summer 2010. 
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Raptors are a group of special interest because of their propensity to fly at heights similar to 

those encompassed by a turbine RSA. Except for turkey vultures during Spring 2010 surveys, 

over all seasons, encounter rates for raptor species were low at less than 0.05 birds flying at RSA 

height/20 min (Tables 6a-r) and less than 0.05 birds flying at RSA height/30 min (Tables 6a-r). 

No raptors were observed flying at the anticipated height of the RSA during winter 2010, early 

summer 2010, late summer 2010 and winter 2010–2011; thereby minimizing the potential for 

negative turbine-related impacts to these species. Raptors are slow-reproducing, long-lived 

species and, as a result, local populations may be sensitive to small changes in adult survival; 

even a few fatalities could have local population implications. The overall low encounter rates of 

raptors at NWTC, however, imply a low likelihood of turbine collisions. 

Of raptor species observed at point count surveys at the NWTC, only turkey vultures, American 

kestrels, red-tailed hawks and ferruginous hawks were observed flying at RSA height during all 

point count surveys and all other raptors were observed flying below the RSA height for the 

three large turbines. Except for turkey vultures, all raptor encounter rates were less than 0.05 

birds flying at RSA height/20 or 30 min (Table 6a-r). Encounter rates for turkey vultures were 

highest at 0.09 birds flying at RSA height/30 min (Table 6h). The ferruginous hawk was 

observed at a height that placed it within RSA height for all three large turbines and the 

encounter rate remained the same (0.01 birds flying at RSA height/30 min; Tables 6b, h, n). 

Turkey vultures, red-tailed hawks, and ferruginous hawks have all been documented as fatalities 

at wind energy facilities (Orloff and Flannery 1992, Thelander et al. 2003, Erickson et al. 2004, 

Stantec 2010, Johnson and Erickson 2010). However, within each season, observed raptors had 

low mean use values of less than 0.30 birds/30 min (Table 3a); thereby minimizing the potential 

for negative turbine-related impacts to these species.

Swainson’s hawks, ferruginous hawks, and northern harriers were observed on the NWTC 

incidental to point count surveys. Additionally, golden eagle, bald eagle, prairie falcon, and 

great-horned owl were observed at off-site locations but not on the NWTC. However, since these 

species were not observed frequently it is unlikely that there is great potential for turbine-related 

impacts to these species. Only red-tailed hawks were observed at the NWTC flying within RSA 

height were discussed previously based upon encounter rates. 

2.6.3 Comparison to Historical Data 

Birds in grasslands 

The grassland birds present on NWTC grasslands in 2001–2002 and 2010–2011 varied and could 

be attributed to changes in precipitation or increased development activity at the site. During 

2001–2002 and 2010–2011, western meadowlark and vesper sparrow were two of the most 

abundant species. In 2010–2011 surveys, red-winged blackbird was one of the most abundant 

species likely due to the presence of water at a small pond south of the NWTC and a small 

wetland near the administration building. The region was in a drought in 2002 (Figure 7) and 

would have been unlikely to support the abundance of red-winged blackbirds seen in 2010–2011. 
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Despite differences between survey periods, western meadowlark, vesper sparrow, and horned 

lark were three of the most abundant species at the off-site grasslands at Boulder County and 

Rocky Flats during 2001–2002 and 2010–2011. 

The most abundant raptors included American kestrel and red-tailed hawk in 2001–2002 and 

2010–2011 surveys at grasslands at the NWTC, Boulder County and Rocky Flats. These resident 

grassland raptor species are expected to continue use of the NWTC despite the continued 

development partially due to the increase in vertical structures that have occurred since the 

2001–2002. 

Birds in Pine Forest 

As previously mentioned, Schmidt et al. (2003) compared pine plots at NWTC-01 to two 

Boulder County point count locations and during 2010–2011 surveys, there were no pine plots 

available for comparison to NWTC-01 at the surveyed Boulder County point count locations 

(CB-01, CB-02, and CB-03). RF-01 was the only reference site with a grouping of pine trees but 

it was not a site originally considered a “pine plot” by Schmidt et al. (2003). This makes a true 

comparison to historical data difficult. However, point count location NWTC-01 was surveyed as 

a pine plot in all survey years. As point count circles were surveyed out to 100 m for non-raptors 

and 200 m for raptors, many of the most abundant birds are grassland birds as the pine plots at 

this location are small. Despite the various differences between years, western meadowlark, 

black-billed magpie, and vesper sparrow were the most abundant non-raptors and red-tailed 

hawks and American kestrels were two of the most abundant raptors during the 2001–2002 and 

the 2010–2011 surveys at the on-site pine plot (NWTC-01). Despite differences between survey 

periods, western meadowlark, vesper sparrow, and black-billed magpie were three of the most 

abundant species at the off-site pine plots during 2001–2002 and 2010–2011. Greater differences 

were seen in the number of species at off-site locations when comparing 2001–2002 surveys to 

2010–2011 surveys. This is attributed to the differences between the original pine plot sites and 

not a change in bird community at the point count locations.

2.6.4 Protected Species 

No federal threatened or endangered species or candidates for listing under the ESA were 

observed during or incidentally to point count surveys. No state threatened or endangered 

species were observed during or incidentally to point count surveys. 

Bald and golden eagles are given federal protection by the BGEPA of 1940 (16 USC 668-668d, 

54 Stat. 250) as amended. Colorado also lists bald eagles as species of concern. Both eagle 

species were observed at Rocky Flats. A single bald eagle was observed during point count 

surveys at RF-02. Golden eagles were observed incidental to surveys near RF-03 and during 

point count surveys at RF-02. No eagles were observed at Boulder County or at the NWTC. Bald 

eagles are typically found near riparian areas or large reservoirs where large fish are present and 

are known to move long distances between foraging areas. Several large reservoirs are present in 
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the area with the largest (Standley Lake) approximately 6 kilometer (km) (3.7 miles) southeast of 

Rocky Flats and it could provide bald eagles with suitable foraging habitat. In previous years, 

Standley Lake has had a nesting pair of bald eagles (CFO 2006). In 2010, a pair of bald eagles 

nested in Coal Creek approximately 4.0 km (2.5 miles) to the northeast (DuWaldt 2010). The 

closest lake (Marshall Lake) that might attract bald eagles to the area is approximately 3.5 km 

(2.2 miles) to the north. Additionally, a known bald eagle nest occurs to the northeast of the 

NWTC and the bald eagle detected may have been from this pair (T. Ryon, Pers. Comm.). 

Because of the low mean use off site (0.01 birds/30 min), it is unlikely that bald eagles will be 

affected by the development of the NWTC as they travel between reservoirs (Table 2c). 

Compared to bald eagles, golden eagles utilize more habitats and have a more diverse diet. The 

undeveloped grasslands surrounding the NWTC would provide a large expanse of foraging 

habitat and the mountains to the west would provide nesting sites. Although it is currently quite 

small due to a recent plague outbreak, the prairie dog colony at CB-01 (Boulder County) will 

likely re-build over time and could be used by golden eagles as a foraging area. Although 

encounter rates were not calculated for birds observed off-site, a single golden eagle was 

observed flying at 5 m high which is not within the RSA of the three large turbines. In addition, 

on-site prairie dogs at the NWTC were re-located in 2009 to the northwestern portion of the site 

but were decimated by a plague outbreak in 2010 (B. Beatty, Pers. Comm.). However, without 

human interference, reestablishment of the prairie dog colony will likely take some time due to 

distance from the currently small colony on Boulder County. The prairie dog colony on the 

NWTC was previously in the northwestern corner of the site where no large turbines are present 

and small turbines are widely spaced. Prairie dog colonies could attract golden eagles to the area; 

however, the distance of the colony to the large turbines reduces the probability of interactions 

with the turbines. During raptor surveys conducted at the NWTC in 2010, no resident golden 

eagles were observed using the NWTC and only two percent of all migrating raptors observed 

were golden eagles (DuWaldt 2010). Because of low mean use offsite (0.02 birds/30 min) and 

the available foraging habitat and prey off site, it is unlikely that golden eagles will be negatively 

affected by the continued development and use of the NWTC (Table 2c). 

In addition to the bald eagle mentioned above, three state species of concern were observed – 

ferruginous hawk, sandhill crane, and long-billed curlew. Ferruginous hawks occur along the 

front range of Colorado year-round. Ferruginous hawks were observed incidentally to and during 

point count surveys at the NWTC but only during the spring and summer seasons (Table 7b). 

Similar to golden eagles, ferruginous hawks forage in arid grasslands for small mammals, mainly 

prairie dogs or ground squirrels. Combining low on-site mean use (0.01 birds/30 min), limited 

prey on site, and available foraging habitat with prey off site, it is thus unlikely that ferruginous 

hawks will be negatively affected by the continued development and use of the NWTC (Table 

2a). Sandhill cranes were only observed during the fall season as a single flock of 4 individuals 

on November 12, 2010. These cranes were flying south and appeared to be migrating. It is 

unlikely that sandhill cranes would stopover within the NWTC due to the lack of preferred 

habitat (e.g., grain fields and small wetlands). It is likely that additional sightings of migrating 
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sandhill cranes may be observed in the future; however, low mean use (0.06 birds/20 min), lack 

of habitat, low encounter rates for all three large turbines (0.06 birds flying at RSA height/20 

min), and no known fatalities of sandhill cranes at wind facilities based on publicly available 

data, indicate that sandhill cranes that migrate through the region are unlikely to be negatively 

affected by the NWTC. Long-billed curlews were only observed at off-site location CB-03 

during spring 2010 (Table 2c). The number of wading birds found at wind farms and 

communications towers is low, suggesting that these taxa avoid these structures (Crawford and 

Engstrom 2001, Erickson et al. 2004, Anderson et al. 2005, Jain et al. 2007). Because long-billed 

curlews were only observed off site and no fatalities of long-billed curlews have been 

documented as fatalities under wind turbines, it is unlikely that long-billed curlews will be 

significantly affected by the development of the site. 

2.6.5 Recommendations 

The greatest potential impact on avian species is direct mortality or injury from collisions with 

turbines and associated guyed meteorological towers and loss of habitat. Tetra Tech recommends 

the following best management practices: 

 The use of lights on turbines should be minimized when practicable in accordance with 

state, federal, and local requirements, because lights may attract migrating birds to the 

vicinity of turbines or met towers, particularly during certain weather conditions (Evans 

et al. 2007). 

 Facility lighting (not turbine or met tower) can also attract birds to the area and increase 

their risk of collision with wind turbines and tower guylines. External lighting at facilities 

(data sheds, buildings, etc.) should be kept at a minimum and should be hooded 

downward. Installation of motion sensors on lights would reduce use of lights when not 

required. 

 Although no raptor nests were documented within the NWTC during surveys, several 

raptor species were present and could nest in the area. To reduce impacts to nesting 

raptors, agencies may recommend timing restrictions for construction or operation 

activities (CDOW 2008). Raptor nests discovered during construction should be mapped 

and flagged. Turbines should be placed as far away from raptor nests as project and 

engineering constraints permit and removal of trees should be avoided. If the nest is 

identified to belong to a species of concern, a designated ‘no disturbance zone’ during the 

construction phase should be implemented (APLIC and USFWS 2005, APLIC 2006). 

 Studies have shown that birds are susceptible to collision with towers and associated guy 

wires (Longcore et al. 2008; Gehring et al. 2011). Therefore, the use of guy wires should 

be minimized if possible. When they are necessary, guy wires should be fitted with bird 

flight diverters or high visibility devices to minimize collisions of diurnal birds by 

making wires more visible to flying birds. 
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 Avoid placing turbines near landscape features that would attract high numbers of 

foraging, migrating, or nesting raptors. These features include ridges, prairie dog towns, 

and large trees. 
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3. AVIAN MONITORING – TRANSECT SURVEYS 

3.1 BACKGROUND 

Concerns have been raised that some grassland bird species may avoid areas near turbines after 

the wind farm is in operation (Drewitt and Langston 2006). For example, at the Buffalo Ridge 

wind energy facility in Minnesota, densities of male songbirds were significantly lower in CRP 

grasslands containing turbines than in CRP grasslands without turbines. It was suggested that the 

reduced density may be due to avoidance of turbine noise and maintenance activities, and 

reduced habitat quality due to the presence of access roads and large gravel pads surrounding the 

turbines though none of these factors were measured or analyzed (Leddy et al. 1999). Reduced 

abundance of grassland songbirds was found within 50 m of a turbine pad for a wind farm in 

Washington and Oregon, but the investigators attributed displacement to the direct loss of habitat 

or reduced habitat quality and not the presence of the turbines (Erickson et al. 2004). Recent 

research at two sites in North and South Dakota (Shaffer and Johnson 2008) suggests that certain 

grassland songbird species may avoid turbines by as much as 200 m. It is not known whether or 

not these avoidance effects are temporary (i.e., the birds may habituate to the presence of 

turbines over time) or permanent. 

3.2 STUDY OBJECTIVES 

Tetra Tech evaluated the spatial distribution of grassland songbirds in relation to vertical 

structures, including wind turbines and met towers, at the NWTC. 

3.3 METHODS 

Transects were established running east-west across the NWTC site and spaced 100 m apart 

(Figure 8). Transects excluded the building areas north of the main entrance road and the 

photovoltaic (PV) array. Transects were walked at a moderate pace while recording observations 

to prevent changes in bird detectability due to possible alarm calls given in response to the 

presence of an observer. Spot mapping was used to record locations of birds during the breeding 

season. As the observer walked along the transect line, locations of each bird seen or heard 

within 50 m of the transect were recorded on a map. Transects were surveyed three times during 

the breeding season (May 1–July 15) between sunrise and 10:00 am when males were most 

actively singing and breeding territories were established. 

3.4 ANALYSIS 

Observations of birds were pooled across all surveys and separated by species to examine the 

distribution of individuals in relation to the wind turbines and met towers. All bird observations 

were geo-referenced to evaluate the approximate location of the bird in relation to the nearest 

turbine or met tower (Figure 8). To determine if birds are located further from turbines than 

expected by a random distribution, random points were generated in ArcGIS (n = 10,000), and 

the spatial distribution of bird observations were compared to the distribution of random 

locations. General habitat types (e.g., pine forest, PV array, building areas, wetlands, etc.) were 
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delineated and removed from the total habitat area deemed suitable for grassland birds. Distances 

of each bird observation and each random location were assigned to distance categories, each 

category corresponding to a distance interval from the nearest turbine (e.g., all locations 0 to 50 

m from the nearest turbine fall into distance category 1, all locations 50 to 100 m from the 

nearest turbine fall into category 2, etc.). To determine whether birds were distributed nonrandomly with respect to turbine locations, a chi-square statistic was calculated using the 

following formula: 

where observed = number of birds observed in distance category i and expected = number of 

random points in distance category i. We used an alpha = 0.05 to determine significance. We 

classified turbines into two groups including small (100 kW or less) and large (greater than 100 

kW). 

3.5 RESULTS 

Grassland bird species at the NWTC included grasshopper sparrow, horned lark, savannah 

sparrow, vesper sparrow, and western meadowlark. Due to small sample sizes, analyses on the 

distribution of grasshopper sparrows and horned larks with respect to installed wind turbines 

could not be conducted. We found no significant patterns in the distribution of birds when 

distance to small turbines was analyzed. Only vesper sparrow show significant spatial patterns 

for large turbines with fewer observations than expected in the 50–100 m category and more 

observations than expected in the 150–200 m, 350–400 m, and 400–450 m categories. 

3.6 DISCUSSION AND RECOMMENDATIONS 

3.6.1 Breeding Bird Density and Distribution 

Grassland bird species at the NWTC included western meadowlark, vesper sparrow, grasshopper 

sparrow, savannah sparrow, and horned lark. Although sample size of these species was limited, 

grassland breeding bird distribution at the NWTC does not appear to be affected by the current 

distribution of turbines at the site. Only vesper sparrow showed significant patterns, the 

inference of the results is limited by the extent (one study site) and duration (one season) of the 

study. Turbines at sites 1.2, 1.4, 1E, 3.1, 3.2, and 3.3 are small turbines (less than 100 kW) and 

require less disturbance or loss of grassland habitat for construction and maintenance. Human 

presence and activity was highest at sites 4.0, 4.1, 4.2, 4.3 and 4.4 where the medium and large 

turbines are situated. Sites 4.1 and 4.0 were under construction during the last year and were still 

in the process of being re-vegetated. However, comparability between turbines is difficult as 

only one turbine of each type is present at NWTC and data only covers one breeding season. 

Many of the turbines at NWTC operate based upon testing needs and do not operate on a regular 

schedule. This variability in the types of turbines and their operating schedule increases the 

difficulty of analyzing possible effects to the avian community present on site. Additional studies 
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on the NWTC and other wind facilities in grassland habitats will help to determine the influence 

of wind turbines and associated structures on grassland breeding birds. 

3.6.2 Recommendations 

A potential impact on avian populations is loss of habitat and displacement associated with 

development of wind energy facilities. Tetra Tech recommends the following best management 

practices: 

 Habitat loss is typically the leading cause of population declines in a number of species 

of concern. Bird species are dependent on the native plants for food, cover, and breeding 

habitat. Degraded vegetative communities or the presence of invasive plant species can 

reduce the amount of available quality habitat for birds in these areas. In order to 

decrease the loss of bird habitat, the following practices are recommended: 

 To the greatest extent possible, minimize impacts to native vegetation and riparian 

areas during design and construction of turbines and associated infrastructure. 

 If native vegetation is disturbed or removed during construction of roads or turbines, 

these areas should be reseeded or planted with native material where appropriate. 

 Minimize fragmentation and habitat disturbance by placing roads, turbines, met 

towers, data sheds, and other infrastructure in a pattern that minimizes habitat 

disturbance 

 To maintain high quality native habitats used by birds, a comprehensive vegetation 

management plan should be developed to prevent the spread of noxious weeds 

throughout the NWTC or adjacent areas during construction and ongoing operations. Any 

area that is disturbed or altered should be managed appropriately to avoid the 

introduction or spread of noxious weed species. This practice is important to reduce 

detrimental impacts to avian habitat. 
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4. AVIAN AND BAT MORTALITY 

4.1 BACKGROUND 

Birds have been identified as a group potentially at risk because of collisions with wind turbines 

and met towers (Erickson et al. 2001, Drewitt and Langston 2006, Arnett et al. 2007, Longcore et 

al. 2008, Gehring et al. 2009, Gehring et al. 2011). Colorado has more than 490 documented bird 

species (CFO 2011) and is situated within the Central Flyway, one of the main migratory routes 

for birds in North America (USFWS 2008). The Central Flyway runs through the central portion 

of the U.S. and, as a consequence, the NWTC. Most birds that move along the Central Flyway 

travel from Canada through the central states, eventually reaching the tropics of South America 

via the Gulf of Mexico (USFWS 2008). The avian community of the NWTC is comprised of 

grassland and forest/shrubland species. The majority of the NWTC is categorized as grassland. 

As indicated earlier in this report, typical grassland species present at the NWTC include western 

meadowlark, vesper sparrow, grasshopper sparrow, savannah sparrow, red-winged blackbird, 

black-billed magpie, and horned lark. Forest and shrubland avian species (spotted towhee, 

mountain chickadee, and northern flicker) were mainly found in the northwestern corner of the 

site among ponderosa pine and small shrub species. Raptors (red-tailed hawk, northern harrier, 

and American kestrel) were also present on site and were often seen using met towers for perch 

sites. 

Bat mortality associated with wind turbine operation has been reported at locations around the 

world, including multiple wind farms in the United States (Durr and Bach 2004; Kunz et al. 

2007b; Arnett et al. 2008). Prior to these studies, bat mortality had also been documented at 

communication towers and tall buildings (Crawford and Baker 1981). The direct causes of bat 

mortality include collision with towers (Crawford and Baker 1981) or moving turbine blades 

(Horn et al. 2008) and pulmonary barotrauma (Baerwald et al. 2008). Colorado has 18 species of 

bat that are known to occur within the state boundary. Of these 18 species, 11 have been 

documented in Jefferson County or neighboring counties. These species include big brown bat, 

Townsend’s big eared bat, hoary bat, silver-haired bat, eastern red bat, little brown myotis, 

fringed myotis, long-legged myotis, western small-footed myotis, long-eared myotis, and 

Brazilian free-tailed bat. Bat species that have been documented at the NWTC include big brown 

bat, hoary bat, silver-haired bat, eastern red bat, fringed myotis, and other unidentified Myotis

species (Walsh 2011). None of these bat species are considered to be threatened or endangered at 

the federal or state level; however, Townsend’s big eared bat is considered a species of concern 

in Colorado. 

4.2 STUDY OBJECTIVES 

To document avian and bat fatalities resulting from interactions with wind turbines and other 

vertical structures (including guy wires) and estimate the annual number of avian and bat 

fatalities attributable to NWTC facilities. 
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4.3 METHODS 

To evaluate fatality estimates at wind energy facilities, protocols for post-construction 

monitoring were established and used in this study. 

Survey plots for the turbines and met towers at NWTC were searched from August 30, 2010, to 

August 31, 2011. Additional turbines and met towers were added to surveys as they were 

installed during this time frame. During the course of the study 12 turbines and 19 associated met 

towers were searched weekly at 11 search plots. Turbines varied in hub height (5–90 m), rotor 

diameter (2–101 m), and capacity (1 kW–3.0 MW). Met towers varied in height (9.1–135 m) and 

number of guy lines (3–36). Since so many types of turbines and met towers are present at the 

NWTC, some met towers and turbines were grouped together in a search plot. These groupings 

were centered on the turbine or met tower and were searched by walking parallel transects 

(Figure 9). If structures were close enough to one another that plots overlap and it was difficult 

or impossible to determine which structure caused a fatality, then the location of the carcass 

relative to the structure and recent wind direction were used to determine the responsible 

structure. Studies at other wind projects (e.g., the Vansycle wind plant [Erickson et al. 2000], the 

Buffalo Ridge wind plant [Johnson et al. 2002, Higgins et al. 1996], the Foote Creek Rim wind 

plant [Young et al. 2003], and the Nine Canyon Wind Project [Erickson et al. 2003b]) indicate 

nearly all fatalities are found within the rotor tip height distance measured along the ground from 

the base of the turbines, with a large majority of bat carcasses found within a distance equal to 50 

percent of the tip height. To maximize the area searched, search plots varied in size at turbines 

and met towers at the NWTC and encompassed the height of the turbine or tower. 

Mortality surveys were conducted in the vicinity of the major structures (met towers including 

guy wires and wind turbines) to determine the level of fatalities that can be attributed to NWTC 

facilities, or to document that no fatalities were found. There are four elements to the mortality 

surveys: (1) standardized carcass searches, (2) observer efficiency trials, (3) carcass persistence 

trials, and (4) an incidental casualty and injured bird reporting system. 

4.3.1 Carcass Searches 

Standardized carcass searches were conducted by personnel trained in proper search techniques. 

Searchers systematically walked parallel transects that were spaced approximately 10 meters 

apart. Carcass searches were conducted approximately once per week during the duration of the 

project. The number of avian and bat fatalities attributable to collision with the wind turbines or 

met towers was estimated based on the number of avian and bat fatalities whose death appears 

related to collision with these structures. All carcasses located within areas surveyed, regardless 

of species, were recorded and a cause of death determined based on inspection of the carcass. If 

another cause of death was not apparent (e.g., power line electrocution, collision with vehicle), 

cause of death was assumed to be turbine or guy-wire-related and the fatality was included in the 

fatality estimate. 
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The condition of each carcass found was recorded using the following condition categories: 

 Intact – a carcass that is completely intact, is not badly decomposed, and shows no sign 

of being fed upon by a predator or scavenger. 

 Scavenged – an entire carcass, which shows signs of being fed upon by a predator or 

scavenger, or a portion(s) of a carcass in one location (e.g., wings, skeletal remains, legs, 

pieces of skin, etc.). 

 Feather Spot – 10 or more feathers or 2 or more primaries at one location indicating 

predation or scavenging of the carcass. 

For all casualties found, data recorded included species, sex and age when possible, date and 

time collected, Global Positioning System (GPS) location, condition (e.g., intact, scavenged, 

feather spot), and any comments that may indicate cause of death. All casualties located were 

photographed as found and to show location in relation to the nearest turbine or met tower 

(Appendix 3). Fatalities found within search areas, but not during scheduled searches, were 

included in the fatality estimates. Casualties or fatalities found in non-search areas were treated 

as incidental discoveries and were included in fatality estimates. 

4.3.2 Observer Efficiency 

Searcher efficiency, the probability that an observer detects a carcass that is available to be found 

during a search, is used to account for imperfect detection and adjust carcass counts. Several 

factors might influence searcher efficiency such as searcher experience, vegetation conditions, 

and carcass size. Searcher efficiency trials were conducted at turbine and met tower locations 

where the carcass searches occurred. Searcher efficiency was estimated by size of carcass and 

season (Summer: June 1–August 31, Fall: Sept 1–Nov 15, Winter: Nov 16–Mar 15, and Spring: 

March 16–May 31). During each season, at least 10 large carcasses and 25 small carcasses were 

placed in the search area throughout the search period. Carcasses used for searcher efficiency 

trials included farm-raised birds and small rabbits to simulate bat carcasses. 

Personnel conducting the scheduled carcass searches did not know when the searcher efficiency 

trials were being conducted or the location of the trial carcasses. All carcasses were placed at 

random locations within areas being searched and were dropped from approximately shoulder 

height to simulate a fall from a turbine strike. Each trial carcass was discreetly marked so that it 

could be identified as a study carcass after it was found. The number and location of the trial 

carcasses found during the carcass search were recorded. The number of carcasses available for 

detection during the standard carcass search was determined after the searcher efficiency trial 

was completed. 

4.3.3 Carcass Persistence 

The objective of carcass persistence trials was to estimate the length of time fatalities remain in 

the search area. Estimates of carcass persistence were used to adjust carcass counts for bias. 
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4-4 October 2011 

Carcass persistence includes removal by scavengers or removal by other means (e.g., grass/brush 

mowing). Carcass persistence trials were conducted during each season (Summer: June 1–

August 31, Fall: Sept 1–Nov 15, Winter: Nov 16–Mar 15, and Spring: March 16–May 31) to 

incorporate seasonal effects associated with scavenger densities and weather conditions. 

Trial carcasses were placed randomly within the central undeveloped area of the NWTC (Figure 

10). Each season, a minimum of 10 carcasses of large birds and 15 small birds or mammals (to 

simulate bats) were distributed resulting in a total of approximately 100 trial carcasses used in 

carcass persistence studies during the year. Experimental carcasses were discreetly marked using 

a piece of tape on one leg for recognition by searchers and other personnel. Individuals used for 

searcher efficiency trials were also used for carcass persistence trials. Personnel conducting the 

carcass persistence trial monitored the trial birds over a 30-day period to determine persistence 

time. Carcasses were checked every day for the first four days, and then on days 7, 10, 14, 21 

and 30. Any remaining trial carcasses were removed and disposed at the end of the 30-day 

period. 

4.3.4 Incidental Casualties 

Incidental casualties included carcasses or injured birds that were discovered during travel 

between plots or outside of the search plots by searchers or by NWTC personnel. Incidental 

observations were recorded on the data sheets and these data were not used in the formal 

analysis; however, a summary of incidental carcasses is presented to provide additional 

information about species found in the local area. 

4.4 ANALYSIS 

4.4.1 Carcass Searches 

Carcass search results are presented as the number and the identified species found as a fatality. 

4.4.2 Searcher Efficiency 

The objective of searcher efficiency is to estimate the number of carcasses detected by the 

searcher as searcher efficiency is highly dependent on the region, vegetation, potential 

scavengers, and species used for the trial. Searcher efficiency is used in fatality estimators to 

provide a more accurate prediction of fatalities to account for fatalities missed by observers 

during standard carcass searches. A bootstrap searcher efficiency estimate was calculated by 

resampling the data for each carcass size for each season 1000 times and obtaining the average 

searcher efficiency and 90 percent confidence interval. 

4.4.3 Carcass Persistence 

Carcass persistence was the average length of time a carcass remained onsite before the carcass 

was removed by scavengers or other means and it is used to adjust fatality counts for bias. The 

average number of days that a carcass remained on site was calculated as: 
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4-5 October 2011 

where ti is the number of days each carcass remained on the study area and k is the number of 

removed trial carcasses. A bootstrap estimate and 90 percent confidence intervals were obtained 

by resampling the data set for each carcass size in each season 1000 times. In the bootstrap 

procedure, the data set is sampled with replacement (the same number can be sampled more than 

once) 1000 times to create 1000 datasets from the original dataset. A bootstrap estimate is 

calculated by taking an average of the value from all the datasets as opposed to a simple mean 

from the original dataset. A 90 percent confidence interval is calculated from the 1000 datasets. 

For this study, all carcass removal trials were terminated at 30 days. 

4.4.4 Determination of Avian and Bat Mortality Estimates 

Bias related to searcher efficiency and carcass persistence render raw carcass counts unreliable. 

Fatalities at wind projects are statistically estimated because searcher efficiency is less than 100 

percent and often carcass persistence is shorter than the search interval. To estimate fatalities, 

we used the Huso estimator (Huso 2010), which has been shown to reduce bias in fatality 

estimates with the following equation: 

k

t

t

k

i

 i

  1

 = 

where is the estimated fatality at the i

th search plot during the jth search in the kth

category and cijk is the observed number of carcasses at the i

th turbine during the jth

search in the k

th category. is a function of the average carcass persistence time, which

was decribed earlier, and the length of the search interval preceeding a carcass being

discrovered. is calculated using the lower value of I, the actual search interval when a

carcass is found or the effective search interval, and is estimated through searcher

efficieny trials previously described. is the proportion of the effective search interval

sampled where = min (1, ). is the estimated probablity that a carcass in the k

th

category that is availble to be found will be found during the j

th search. and

are assumed not to differ among turbines but can differ with carcass size and season.

To obtain an estimate of the number of fatalities the following equation is used: 
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4-6 October 2011 

where ni is the number of searches at plot i (i = 1,..., 12) and t is the effective number of plots 

searched. The equation corrects for searcher efficiency and carcass persistence time. Low 

searcher efficiency results in a higher estimated number of fatalities than were found. Similarly, 

if carcass persistence time is shorter than the fatality search interval, the estimated number of 

fatalities will be higher than the number of carcasses found. 

Due to data limitations, a fatality estimate was obtained for fall and winter using 10 search plots 

and for spring and summer using 11 search plots. As searcher efficiency data was absent in fall 

and limited for bats, one estimate for searcher efficiency and carcass persistence time was 

calculated and used to estimate fatalities. Because the data were pooled among categories, any 

variation in searcher efficiency and carcass persistence was lost. Thus, the one estimate likely 

resulted in an under estimate of fatalities for small birds because the searcher efficiency for this 

group was lower than the overall estimate and an over estimate for large birds because the 

searcher efficiency for this group was higher than the overall estimate. 

4.5 RESULTS 

This section describes fatality monitoring results and provides adjusted fatality estimates based 

on results of the searcher efficiency and carcass persistence trials.

4.5.1 Carcass Searches 

A total of 5 avian carcasses representing 3 species and 2 carcasses that were unable to be 

identified to species were found during the duration of the project. Avian fatalities were found in 

every season except winter (fall – one fatality, spring – one fatality, summer – three fatalities). 

These fatalities included black-billed magpie, mourning dove, red-winged blackbird, an 

unknown sparrow, and an unknown passerine. Except for the unknown passerine from Site 4.3, 

all other species were discovered underneath met towers (M2, 3.4, 4.0, and 4.4; Figure 11). No 

avian species classified as federal endangered or threatened, state endangered or threatened, or 

state species of concern were found as discovered injured or found as fatalities during the 

project. One injured Swainson’s hawk was discovered within the search plots; however, no 

raptor fatalities were discovered within search plots. 

A total of 13 bat carcasses were found representing 3 identified species (11 carcasses), and 2 bats 

that could not be identified to species during the standard carcass searches. Bat fatalities were 

found only during summer and fall seasons (summer – fifteen fatalities, fall – six fatalities). The 

bat species found as fatalities were hoary bat (5 fatalities), silver-haired bat (3 fatalities), and big 

brown bat (3 fatalities). No bat species classified as federal endangered or threatened, state 

endangered or threatened, or state species of concern were found as fatalities during the project. 

Bat carcasses were only found at site 4.1 (7 carcasses) and site 4.4 (6 carcasses; Figure 11). 

4.5.2 Observer Efficiency 

Of the 107 carcasses (31 large, 76 small) that were placed at turbine and met tower sites during 

searcher efficiency trials (winter, spring and summer), the searcher found 52. As it was unknown 
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4-7 October 2011 

if these carcasses were present during the searcher efficiency trial, an adjusted searcher 

efficiency was calculated to incorporate this. Overall searcher efficiency was estimated at 49 

percent (90 percent CI: 40–56 percent; Table 9). In 2001–2002, overall searcher efficiency was 

41.5 percent and when adjusted for unrecovered carcasses searcher efficiency was calculated to 

be 56.7 percent (Schmidt et al. 2003). 

4.5.3 Carcass Persistence 

A total of 77 carcasses (30 large and 47 small) were placed in the field during carcass persistence 

trials during three seasons (winter, spring, summer). Pooled carcass persistence was estimated at 

24.8 days (90 percent CI: 19.08–32.86) over all seasons (Table 9). Mean persistence for small 

carcasses during summer was likely overestimated. Two small carcasses were considered to have 

persisted the entire 30 day period even though only a single leg remained. The legs associated 

with these carcasses were ones that had been marked with masking tape for identification and 

were likely rejected by the scavenger. Without the remains of the leg, the carcasses would have 

been considered removed by day 10 or earlier. This would have decreased the amount of days 

carcasses persisted; thereby, increasing the mortality estimate. Estimate for average mean 

persistence across seasons was 16.3 days (19.2 for large birds and 14.4 for small birds/bats). 

During the three carcass persistence trials (winter, summer, spring), approximately 33 percent of 

placed carcasses remained over the course of the trials. Schmidt et al. 2003 conducted four 

carcass persistence trials for 21 days using 10 carcasses during each trial and estimated that 

approximately half remained at end of trials. 

4.5.4 Incidental Casualties 

Two avian carcasses were found incidentally – a barn swallow and a raven – by NREL staff near 

the NWTC administration building. Eight bat carcasses were found incidentally – big brown bat 

(2 carcasses), hoary bat (3 carcasses), silver-haired bat (2 carcasses) and Myotis species (1 

carcass) – by NREL staff or during the initial clearing of fatality search plots. An injured 

Swainson’s hawk was discovered by NWTC staff on August 5, 2011 at Site 4.1. The Swainson’s 

hawk was transported by NREL personnel to the Birds of Prey Foundation (Boulder, CO) for 

treatment of fracture in the right carpals and rehabilitation. As of September 2011, the 

Swainson’s hawk was reported to be recovering well and expected to be released later in the fall 

for migration or spring 2012. 

4.5.5 Protected Species 

No federal threatened or endangered and state threatened or endangered species were found as 

fatalities during carcass searches or incidentally within the NWTC. No Colorado species of 

concern were found as fatalities during carcass searches or incidentally within the NWTC. 

4.5.6 NWTC Avian and Bat Mortality Estimate 

Due to the small sample size of seasonal data, the estimate of total number of turbine-related 

fatalities was only able to be estimated for fall/winter season and spring/summer season. Annual 
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4-8 October 2011 

fatality rates were unable to be estimated due to differences in the number of search plots during 

different times of the study. However, given the same statistical methods were used to estimate 

fatalities for both seasons, a coarse estimate of annual fatalities could be obtained by summing 

the seasonal values. Based upon 2010–2011 fatalities, searcher efficiency trials, and carcass 

persistence trials, 3 avian fatalities (90 percent CI: 2–8) and 16 bat fatalities (90 percent CI: 13–

49) are estimated to occur on the NWTC site during fall/winter seasons (Table 10). During 

spring/summer seasons, 10 avian fatalities (90 percent CI: 5–17) and 17 bat fatalities (90 percent 

CI: 3–45) are estimated to occur on the NWTC site (Table 10). 

4.6 DISCUSSION AND RECOMMENDATIONS 

4.6.1 Discussion 

The fatality monitoring program established at the NWTC was designed to document whether or 

not mortalities associated with aerial structures and guywires are occurring at the NWTC, and to 

provide estimates of annual avian and bat fatality rates that are comparable to the preconstruction survey (Schmidt et al. 2003) and post-construction surveys at other wind energy 

facilities. Based on the development of the site during the 2001–2002 study, Schmidt et al. 

(2003) estimated 24 avian fatalities would occur on the NWTC annually. However, estimators of 

fatalities have been improved since the pre-construction surveys of the large turbines at the 

NWTC. As stated by Huso (2010), “failure to use an unbiased estimator precludes direct 

comparability of results among studies and even within studies”. Because of the differences in 

estimators, direct comparisons of estimates are difficult and due to the unique situation of the 

NWTC as a test facility with turbines and met towers in close proximity and changing over time, 

fatality estimates are provided on a seasonal per search plot basis. 

During fall/winter seasons, fatalities of 0.22 birds/search plot and fatalities of 1.45 bats/search 

plot are estimated to occur on the NWTC site (Table 10). During spring/summer seasons, 

fatalities of 0.85 birds/search plot and fatalities of 1.53 bats/search plot are estimated to occur on 

the NWTC site (Table 10). Annual fatality estimates in the Rocky Mountain region are 1.5 

birds/turbine/year and 1.2 bats/turbine/year (NWCC 2004). However, these estimates are based 

on a limited sample size of 2 studies. Ninety-percent bootstrap confidence intervals for seasonal 

avian fatalities at NWTC (fall/winter: 0.19–0.66 birds/search plot; spring/summer 0.38–1.47 

birds/search plot) were lower than the Rocky Mountain regional estimate. Fatality estimates for 

bats in the Rocky Mountain region are within the calculated confidence interval of bats/search 

plot at NWTC (fall/winter: 1.15–4.43, spring/summer: 0.19–4.04). Although fatality estimates 

were similar to regional estimates, additional installation of multi-megawatt turbines are likely to 

cause an increase in the total site fatalities as the majority of fatalities during the 2010–2011 

search were found near large turbines and their related met towers. 

Migrant passerines (e.g., songbirds) are found more often in post-construction mortality 

monitoring compared to other groups of birds (Arnett et al. 2007; Erickson 2007). In fact, at 

newer generation wind energy facilities outside of California, approximately 80 percent of 
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4-9 October 2011 

documented mortalities have been songbirds, of which 50 percent are often nocturnal migrants 

(Erickson et al. 2001, Drewitt and Langston 2006, Johnson et al. 2002, Strickland and Morrison 

2008). This suggests that fatalities may be concentrated during spring and fall avian migrations. 

A total of 5 avian carcasses were found during standard carcass searches; however, all species 

detected were local breeding species and were found during fall, spring and summer seasons. 

Locally breeding songbirds typically experience lower mortality rates than migrants because 

many of these species tend not to fly at the height of the turbine rotor during the breeding season. 

Similar to the avian fatalities (underneath guy wires of met towers – 3, at turbine base – 1) 

reported by Schmidt et al. (2003), the majority of avian fatalities found during carcass searches 

during 2010–2011 were underneath met towers (4) with a single carcass found at the base of a 

turbine. Although the close proximity of turbines and met towers on the NWTC makes 

determining which vertical structure caused the fatality difficult, the 2010–2011 results appear to 

support those found by Schmidt et al. and suggest that the guyed met towers (19) will continue to 

cause higher amounts of avian fatalities than the installed turbines (12) despite the recent 

installation of three large turbines. Similar to NWTC results, the Foote Creek Rim Windpower 

Project in Carbon County, Wyoming also had higher amounts of fatalities associated with the 5 

guyed towers (38 m) on site than the 69 turbines (600 kW; Young et al. 2003). Although Gehring 

et al. (2011) documented that guyed towers have higher fatalities than unguyed towers, tower 

height, lighting and local weather conditions also influence fatality rates (Longcore et al. 2008, 

Gehring et al. 2011). As sites were not searched every day, the influence of local weather 

conditions was not always known. However, the unknown sparrow found at site 4.4 met tower 

was discovered after some low lying clouds had passed through the area. Although tall, guyed 

met towers may have higher fatality rates than unguyed structures it is important to note that 

even though many guyed met towers (19) are installed at the NWTC, fatality rates for the site 

were still low. A recent study has shown that despite the seemingly high number of avian 

collisions that occur with towers and wind turbines, these fatalities have no apparent impact on 

long-term population trends (Arnold and Zink 2011). 

With the exception of the American kestrel feathers found incidentally while traveling between 

search plots, there was no evidence of any raptor fatalities during standard carcass searches. This 

is consistent with the findings of Schmidt et al. 2003 and the prediction that raptor fatalities were 

expected to be low. Raptor fatalities are still expected to be low based on the fatality monitoring 

provided no changes occur in the study area that influence raptor use. 

Bat fatalities at wind farms are highest during mid to late summer and early fall and tend to 

involve migratory tree roosting species, such as the hoary bat, silver-haired bat, and eastern red 

bat (Cryan and Barclay 2009). Peaks in fatality rates appear to coincide with increasing bat 

activity levels associated with southward migration (Arnett et al. 2009). These conclusions hold 

true with fatalities found at the NWTC. Walsh (2011) documented that bat activity was highest 

from mid-July to mid-September at the NWTC which is when the majority of bat fatalities were 

found. Of the bat carcasses found during 2010–2011, all were found during mid-summer to early 
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4-10 October 2011 

fall (30 August–13 September 2010 and 15 June–2 September 2011) occurring during the peak 

of bat migration. Unlike avian fatalities, bat fatalities had a limited distribution and were only 

found at site 4.4 (6 carcasses, 2 species, 2 unknowns) and at site 4.1 (7 carcasses, 3 species). 

During the 2001–2002 study, no bat carcasses were found at the NWTC search plots (Schmidt et 

al. 2003). However, configuration of the NWTC site in 2001–2002 did not include turbines at 

site 4.1 (installed during 2010–2011) or site 4.4 (installed in 2009). Schmidt et al. (2003) also 

conducted acoustical bat studies and concluded that the northwestern corner of the NWTC 

appeared to have the most bat activity due to the ponderosa pine trees that provided foraging and 

possible roosting habitat. The drainages south of site 4.4 and between sites 4.0 and 4.1 could also 

provide foraging habitat especially when water is present. Additionally, on Rocky Flats, less than 

1 km south of site 4.4, there is an old barn which could also provide roosting habitat for bats. 

Acoustical bat studies were also conducted at the NWTC during 2010. However, this included 

only a single detector placed in the location Schmidt et al. (2003) had previously determined to 

have the most bat activity. Therefore, no information was given to determine the number of bat 

passes near the large turbines at sites 4.1 or 4.4 where the bat fatalities occurred. Since turbine 

testing and not energy production is the main goal for the NWTC, measures can be taken to 

reduce the potential for fatalities, especially for bats, by increasing turbine cut-in speeds during 

times when bats would be most active (i.e., dusk, migration periods; Arnett 2011). 

4.6.2 Recommendations 

The greatest potential impact on avian and bat species is direct mortality or injury from collisions 

with turbines and associated guyed met towers. Tetra Tech recommends the following best 

management practices: 

 Studies have shown that birds are susceptible to collision with towers and associated guy 

wires (Longcore et al. 2008; Gehring et al. 2011). Therefore, the use of guy wires should 

be minimized if possible. When they are necessary, guy wires should be fitted with bird 

flight diverters or high visibility devices to minimize collisions of diurnal birds by 

making wires more visible to flying birds. For maximum benefit the use of such diverters 

should be considered during met tower design and planning. 

 The use of lights on turbines and met towers should be minimized when practicable in 

accordance with state, federal, and local requirements, because lights may attract 

migrating birds to the vicinity of turbines or met towers, particularly during certain 

weather conditions (Evans et al. 2007). Steady burning lights appear to increase collisions 

of migratory birds and should be removed when practicable to minimize collisions 

(Gehring et al. 2009). 

 Bat fatalities often occur during low wind speeds (less than 13 mph) when bats are 

actively foraging. Studies have shown that increasing turbine cut-in speed (greater than 

13 mph), especially during times when bats would be most active (i.e., dusk, migration 
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4-11 October 2011 

periods from August – early October) can reduce bat mortalities by approximately 50 

percent or more (Arnett 2011). 

 Standard protocol for handling injured wildlife should be developed and distributed to all 

those working at NWTC. Protocols should include a NWTC contact; list of wildlife 

rehabilitators for bats, raptors, and other birds; health and safety measures; and 

information on any required permits. Not all wildlife rehabilitators can take all species. 

 
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Evans, W.R., Y. Akashi, N.S. Altman, and A.M. Manville, II. 2007. Response of night-migrating 

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Avian Monitoring and Mortality Report 

National Wind Technology Center 

5-4 October 2011 

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mortality at the Buffalo Ridge Windplant, MN. KENETECH Windpower, Inc., Cooperative 

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Huso, M.M.P. 2010. An estimator of wildlife fatality from observed carcasses. Environmetrics 

22:318-329.

Jain, A., P. Kerlinger, R. Curry, and L. Slobodnik. 2007. Annual report for the Maple Ridge 

wind power NWTC post-construction bird and bat fatality study—2006. Prepared by Curry 

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for the Maple Ridge NWTC. 

Johnson, G. D. and W.P. Erickson. 2010. Avian, Bat and Habitat Cumulative Impacts Associated 

with Wind Energy Development in the Columbia Plateau Ecoregion of Eastern Washington 

and Oregon. Prepared by West, Inc. for Klickitat County, Washington. 

Johnson, G.D., W.P. Erickson, M.D. Strickland, M.F. Shepherd, D.A. Shepherd, and S.A. 

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Strickland, R.W. Thresher, and M.D. Tuttle. 2007. Ecological impacts of wind energy 

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Avian Monitoring and Mortality Report 

National Wind Technology Center 

5-5 October 2011 

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National Wind Technology Center 

5-6 October 2011 

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and Wildlife Service, Division of Migratory Bird Management, Arlington, Virginia. 

Available online at: http://www.fws.gov/migratorybirds/ 

USFWS. 2008b. Flyways. Retrieved from: http://flyways.us/flyways/info. 

USGS (U.S. Geological Survey). 2011. Bat population database. Available online at: 

http://www.fort.usgs.gov/BPD/default.asp. 

Walsh Environmental Scientists and Engineers (Walsh). 2011. Bat Acoustical Surveys at the 

National Renewable Energy Laboratory, National Wind Technology Center, Jefferson 

County, Colorado. Prepared for the National Renewable Energy Laboratory. Golden, CO. 

Western Ecosystems Technology, Inc. (WEST). 2009. Study Plan, Monitoring Avian Use and 

Mortality. Prepared for National Renewable Energy Laboratory, National Wind Technology 

Center. Golden, CO. 

Young, D.P., Jr., W.P. Erickson, R.E. Good, M.D. Strickland, and G.D. Johnson. 2003. Avian 

and bat mortality associated with the initial phase of the Foote Creek Rim Wind Power 

NWTC, Carbon County, Wyoming: November 1998 - June 2002. Technical Report prepared 

by WEST, Inc. for Pacificorp, Inc., SeaWest Windpower, Inc. and Bureau of Land 

Management. 
Avian Monitoring and Mortality Report 

National Wind Technology Center 

 October 2011 

FIGURES 
!

!

!

!

!

!

!

!

!

!

!

Project Boundary

287

6

36

36

287

40

278

287

7

72

72

58

46

121

128

93

95

391

93

119

25

70

76

25

25

D

Boulder

Lafayette

Louisville

Broomfield

N

Federal

Heights

Westminster

Arvada 

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Golden
")

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93

128

CB1

CB2

CB3

RF1

RF2

RF3

NW1

NW2

NW3

NW4

NW5

NW6
0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

Mean Use (birds/30 min)

Survey Date

Figure 3a. Non-raptor mean use by survey date at the National Wind Technology Center, 30-minute point count surveys.

Winter 2010 Spring 2010 Summer 2010
0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Mean Use (birds/20 min)

Survey Date

Figure 3b. Non-raptor mean use by survey date at the National Wind Technology Center, 20-minute point count surveys.

Summer 2010 Fall 2010 Winter 2010 - 2011
0.0

5.0

10.0

15.0

20.0

25.0

Mean Use (birds/30 min)

Survey Date

Figure 3c. Non-raptor mean use by survey date at Rocky Flats NWR and Boulder County Open Space, 30-minute point count surveys. 

Winter 2010 Spring 2010 Summer 2010
0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

Mean Use (birds/20 min)

Survey Date

Figure 3d. Non-raptor mean use by survey date at Rocky Flats NWR and Boulder County Open Space, 20-minute point count surveys.

Summer 2010 Fall 2010 Winter 2010 - 2011
1.70

0.00

0.90

0.40

0.20

0.60

3.83

2.83

3.00

2.58

3.25

3.58

6.67

2.67

5.33

5.67

7.50

6.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Mean use birds/30 min.

Point Number

Figure 4a. Non-raptor mean use by point at the National Wind Technology Center, 30-minute point count surveys.

Winter 2010

Spring 2010

Summer 2010
12.57

27.00

9.00

9.57

9.00

8.00

4.92

4.83

1.10

2.75

1.75

2.44

1.00

1.20

0.80

0.20

0.33

3.20

0.00

5.00

10.00

15.00

20.00

25.00

30.00

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Mean use birds/20 min.

Point Number

Figure 4b. Non-raptor mean use by point at the National Wind Technology Center, 20-minute point count surveys.

Summer 2010

Fall 2010

Winter 2010-2011
0.44

0.67

2.22

4.00

0.44

1.89

7.83

7.58

7.83

15.25

4.75

5.75

2.00

1.00

1.50

0.50

1.00

2.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Mean use birds/30 min.

Point Number

Figure 4c. Non-raptor mean use by point at Rocky Flats NWR and Boulder County Open Space, 30-minute point count surveys. 

Winter 2010

Spring 2010

Summer 2010
10.42

10.14

16.71

6.50

8.71

4.28

3.25

6.67

5.75

3.00

5.82

3.18

0.17

0.40

0.33

0.50

0.20

3.60

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Mean use birds/20 min.

Point Number

Figure 4d. Non-raptor mean use by point at Rocky Flats NWR and Boulder County Open Space, 20-minute point count surveys.

Summer 2010

Fall 2010

Winter 2010-2011
0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

Mean Use (birds/30 min)

Survey Date

Figure 5a. Raptor mean use by survey date at the National Wind Technology Center, 30-minute point count surveys.

Winter 2010 Spring2010 Summer 2010
0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

Mean Use (birds/20 min)

Survey Date

Figure 5b. Raptor mean use by survey date at the National Wind Technology Center, 20-minute point count surveys.

Summer 2010 Fall 2010 Winter 2010 - 2011
0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Mean Use (birds/30 min)

Survey Date

Figure 5c. Raptor mean use by survey date at Rocky Flats NWR and Boulder County Open Space, 30-minute point count surveys. 

Winter 2010 Spring 2010 Summer 2010
0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

Mean Use (birds/20 min)

Survey Date

Figure 5d. Raptor mean use by survey date at Rocky Flats NWR and Boulder County Open Space, 20-minute point count surveys.

Summer 2010 Fall 2010 Winter 2010 - 2011
0.00

0.40

0.10

0.20

0.40

0.00

0.83

0.42

0.08

0.17

0.000.00

0.33

0.67

0.00

0.67

0.000.00

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Mean use birds/30 min. 

Point Number

Figure 6a. Raptor mean use by point at the National Wind Technology Center, 30-minute point count surveys.

Winter 2010

Spring 2010

Summer 2010
0.00

0.14

0.000.000.000.00

0.17

0.00

0.10

0.17

0.13

0.22

0.000.000.00

0.40

0.000.00

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Mean use birds/20 min. 

Point Number

Figure 6b. Raptor mean use by point at the National Wind Technology Center, 20-minute point count surveys.

Summer 2010

Fall 2010

Winter 2010-2011
0.33

0.000.00

0.33

0.110.11

0.25

0.17

0.08

0.330.33

0.08

0.000.000.00

1.50

0.000.00

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Mean use birds/30 min. 

Point Number

Figure 6c. Raptor mean use by point at the Rocky Flats NWR and Boulder County Open Space, 30-minute point count surveys. 

Winter 2010

Spring 2010

Summer 2010
0.00

1.00

0.000.00

0.14

0.00

0.17

0.500.50

0.00

0.09

0.00

0.17

0.00

0.17

0.33

0.200.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Mean use birds/20 min. 

Point Number

Figure 6d. Raptor mean use by point at the Rocky Flats NWR and Boulder County Open Space, 20-minute point count surveys.

Summer 2010

Fall 2010

Winter 2010-2011
Figure 7. Palmer Drought Severity Index (PDSI) for Colorado Platte Drainage Basin, including the National Wind Technology Center, from January 2000 

to May 2011. PDSI values: -4.0 or less (Extreme Drought), -3.0 or -3.9 (Severe Drought), -2.0 or -2.9 (Moderate Drought), -1.9 to +1.9 (Near Normal), 

+2.0 or +2.9 (Unusual Moist Spell), +3.0 or +3.9 (Very Moist Spell), +4.0 or above (Extremely Moist). 
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Avian Monitoring and Mortality Report 

National Wind Technology Center 

October 2011 

TABLES 

 
Survey Number Date(s)

7DEOH 1D. National Wind Technology Center 30-minute point count survey dates.

Winter 2010

1 1/13/10

2 1/22/10

3 1/29/10

4 2/2/10

5 2/11/10

6 2/17/10

7 2/24/10

8 3/4/10

9 3/11/10

10 3/17/10

Spring 2010

1 3/26/10

2 4/8/10

3 4/14/10

4 4/22/10

5 4/29/10

6 5/5/10

7 5/13/10

8 5/21/10

9 5/28/10

10 6/4/10

11 6/11/10

12 6/17/10

Summer 2010

1 6/23/10-6/24/10

2 7/2/10

3 7/8/10
Survey Number Date(s)

Table 1b. National Wind Technology Center 20-minute point count survey dates (a).

Summer 2010

1 7/16/10

2 7/20/10

3 7/29/10

4 8/3/10

5 8/12/10

6 8/19/10

7 8/27/10

Fall 2010

1 9/2/10

2 9/9/10

3 9/16/10

4 9/23/10

5 9/30/10

6 10/6/10

7 10/14/10

8 10/20/10

9 10/28/10

10 11/4/10

11 11/12/10

12 11/18/10

Winter 2010-2011

1 12/7/10

2 12/15/10

4 1/12/11

5 1/23/11-1/26/11

6 2/10/11-2/14/11
Species

Winter 2010 Spring 2010

7DEOH2a. Avian species observed during 30-minute point count surveys at the National Wind Technology Center, 2010.

Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

western meadowlark 6 5 0.10 84 74 1.17 26 26 1.53 116 105 0.78

vesper sparrow 0 0 0.00 50 29 0.69 33 28 1.94 83 57 0.56

barn swallow 0 0 0.00 13 4 0.18 9 2 0.53 22 6 0.15

black-billed magpie 9 5 0.15 9 6 0.13 0 0 0.00 18 11 0.12

common raven 4 3 0.07 9 7 0.13 1 1 0.06 14 11 0.09

American robin 3 2 0.05 8 8 0.11 3 3 0.18 14 13 0.09

Brewer's blackbird 0 0 0.00 13 7 0.18 0 0 0.00 13 7 0.09

red-tailed hawk 7 6 0.12 3 3 0.04 2 1 0.12 12 10 0.08

European starling 0 0 0.00 11 6 0.15 1 1 0.06 12 7 0.08

turkey vulture 0 0 0.00 7 3 0.10 3 3 0.18 10 6 0.07

spotted towhee 0 0 0.00 6 5 0.08 3 3 0.18 9 8 0.06

American kestrel 3 3 0.05 6 6 0.08 0 0 0.00 9 9 0.06

mountain bluebird 8 1 0.13 0 0 0.00 0 0 0.00 8 1 0.05

western kingbird 0 0 0.00 2 1 0.03 4 3 0.24 6 4 0.04

mallard 0 0 0.00 6 5 0.08 0 0 0.00 6 5 0.04

Wilson's snipe 0 0 0.00 1 1 0.01 3 2 0.18 4 3 0.03

red-winged blackbird 0 0 0.00 4 3 0.06 0 0 0.00 4 3 0.03

black-capped chickadee 4 1 0.07 0 0 0.00 0 0 0.00 4 1 0.03

Say's phoebe 0 0 0.00 2 2 0.03 1 1 0.06 3 3 0.02

horned lark 0 0 0.00 1 1 0.01 2 1 0.12 3 2 0.02

grasshopper sparrow 0 0 0.00 0 0 0.00 3 3 0.18 3 3 0.02

* Mean use=# birds/30 min.
Species

Winter 2010 Spring 2010

7DEOH2a. Avian species observed during 30-minute point count surveys at the National Wind Technology Center, 2010.

Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

downy woodpecker 3 2 0.05 0 0 0.00 0 0 0.00 3 2 0.02

dark-eyed junco 1 1 0.02 2 1 0.03 0 0 0.00 3 2 0.02

American goldfinch 0 0 0.00 1 1 0.01 2 1 0.12 3 2 0.02

Eurasian collared-dove 0 0 0.00 2 1 0.03 0 0 0.00 2 1 0.01

rough-legged hawk 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

northern harrier 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

mourning dove 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

loggerhead shrike 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

killdeer 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

house finch 0 0 0.00 0 0 0.00 1 1 0.06 1 1 0.01

ferruginous hawk 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

common grackle 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

broad-tailed hummingbird 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

blue jay 0 0 0.00 0 0 0.00 1 1 0.06 1 1 0.01

brown-headed cowbird 0 0 0.00 0 0 0.00 1 1 0.06 1 1 0.01

Grand Total 49 30 0.82 247 181 3.43 99 82 5.82 395 293 2.65

* Mean use=# birds/30 min.
Species

Summer 2010 Fall 2010

Table 2b. Avian species observed during 20-minute point count surveys at the National Wind Technology Center, 2010-2011.

Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

western meadowlark 72 65 1.85 29 25 0.46 0 0 0.00 101 90 0.78

red-winged blackbird 99 11 2.54 0 0 0.00 0 0 0.00 99 11 0.76

horned lark 47 39 1.21 20 15 0.32 3 1 0.11 70 55 0.54

grasshopper sparrow 53 33 1.36 15 11 0.24 0 0 0.00 68 44 0.52

western kingbird 46 32 1.18 2 1 0.03 0 0 0.00 48 33 0.37

vesper sparrow 37 32 0.95 4 3 0.06 0 0 0.00 41 35 0.32

Brewer's blackbird 29 8 0.74 10 1 0.16 0 0 0.00 39 9 0.30

song sparrow 7 7 0.18 24 17 0.38 0 0 0.00 31 24 0.24

black-billed magpie 1 1 0.03 11 8 0.17 19 8 0.68 31 17 0.24

barn swallow 16 14 0.41 10 7 0.16 0 0 0.00 26 21 0.20

mourning dove 11 11 0.28 14 8 0.22 0 0 0.00 25 19 0.19

tree swallow 22 8 0.56 0 0 0.00 0 0 0.00 22 8 0.17

chipping sparrow 20 20 0.51 0 0 0.00 0 0 0.00 20 20 0.15

Say's phoebe 15 13 0.38 3 3 0.05 0 0 0.00 18 16 0.14

American goldfinch 3 3 0.08 11 8 0.17 0 0 0.00 14 11 0.11

common raven 6 5 0.15 0 0 0.00 7 7 0.25 13 12 0.10

red-tailed hawk 1 1 0.03 4 3 0.06 1 1 0.04 6 5 0.05

unidentified sparrow 0 0 0.00 5 5 0.08 0 0 0.00 5 5 0.04

northern flicker 0 0 0.00 4 4 0.06 1 1 0.04 5 5 0.04

downy woodpecker 0 0 0.00 5 3 0.08 0 0 0.00 5 3 0.04

Brewer's sparrow 0 0 0.00 5 3 0.08 0 0 0.00 5 3 0.04

* Mean use=# birds/20 min.
Species

Summer 2010 Fall 2010

Table 2b. Avian species observed during 20-minute point count surveys at the National Wind Technology Center, 2010-2011.

Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

unidentified bird 1 1 0.03 3 2 0.05 0 0 0.00 4 3 0.03

sandhill crane 0 0 0.00 4 1 0.06 0 0 0.00 4 1 0.03

mountain chickadee 0 0 0.00 2 2 0.03 2 2 0.07 4 4 0.03

American tree sparrow 0 0 0.00 4 3 0.06 0 0 0.00 4 3 0.03

American kestrel 0 0 0.00 3 3 0.05 1 1 0.04 4 4 0.03

American crow 0 0 0.00 4 4 0.06 0 0 0.00 4 4 0.03

unidentified songbird 0 0 0.00 2 2 0.03 1 1 0.04 3 3 0.02

Townsend’s solitaire 3 1 0.08 0 0 0.00 0 0 0.00 3 1 0.02

loggerhead shrike 2 2 0.05 1 1 0.02 0 0 0.00 3 3 0.02

gray catbird 1 1 0.03 2 2 0.03 0 0 0.00 3 3 0.02

broad-tailed hummingbird 3 3 0.08 0 0 0.00 0 0 0.00 3 3 0.02

black-capped chickadee 3 3 0.08 0 0 0.00 0 0 0.00 3 3 0.02

European starling 2 2 0.05 0 0 0.00 0 0 0.00 2 2 0.02

dark-eyed junco 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.02

sharp-shinned hawk 0 0 0.00 1 1 0.02 0 0 0.00 1 1 0.01

house finch 1 1 0.03 0 0 0.00 0 0 0.00 1 1 0.01

Eurasian collared-dove 1 1 0.03 0 0 0.00 0 0 0.00 1 1 0.01

American robin 0 0 0.00 1 1 0.02 0 0 0.00 1 1 0.01

Grand Total 502 318 12.87 205 149 3.25 35 22 1.25 742 489 5.71

* Mean use=# birds/20 min.
Species

Winter 2010 Spring 2010

Table 2c. Avian species observed during 30-minute point count surveys at off-site reference locations, 2010.

Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

red-winged blackbird 2 1 0.04 132 14 1.83 0 0 0.00 134 15 0.97

western meadowlark 1 1 0.02 121 79 1.68 9 9 0.75 131 89 0.95

horned lark 26 15 0.48 69 25 0.96 0 0 0.00 95 40 0.69

vesper sparrow 0 0 0.00 65 29 0.90 4 5 0.33 69 34 0.50

Franklin’s gull 0 0 0.00 40 1 0.56 0 0 0.00 40 1 0.29

Canada goose 25 1 0.46 4 4 0.06 0 0 0.00 29 5 0.21

American pipit 0 0 0.00 23 3 0.32 0 0 0.00 23 3 0.17

American crow 0 0 0.00 21 4 0.29 0 0 0.00 21 4 0.15

black-billed magpie 13 5 0.24 7 5 0.10 0 0 0.00 20 10 0.14

mountain bluebird 6 1 0.11 12 2 0.17 0 0 0.00 18 3 0.13

common raven 10 7 0.19 6 4 0.08 1 1 0.08 17 12 0.12

cedar waxwing 0 0 0.00 16 2 0.22 0 0 0.00 16 2 0.12

European starling 3 1 0.06 12 4 0.17 0 0 0.00 15 5 0.11

American robin 0 0 0.00 12 7 0.17 0 0 0.00 12 7 0.09

barn swallow 0 0 0.00 11 4 0.15 0 0 0.00 11 4 0.08

red-tailed hawk 4 3 0.07 3 2 0.04 1 1 0.08 8 6 0.06

American kestrel 0 0 0.00 5 5 0.07 2 2 0.17 7 7 0.05

mallard 0 0 0.00 5 4 0.07 0 0 0.00 5 4 0.04

long-billed curlew 0 0 0.00 5 1 0.07 0 0 0.00 5 1 0.04

mourning dove 0 0 0.00 3 2 0.04 1 1 0.08 4 3 0.03

common grackle 0 0 0.00 4 3 0.06 0 0 0.00 4 3 0.03

* Mean use=# birds/30 min.
Species

Winter 2010 Spring 2010

Table 2c. Avian species observed during 30-minute point count surveys at off-site reference locations, 2010.

Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

Wilson's snipe 0 0 0.00 3 2 0.04 0 0 0.00 3 2 0.02

western kingbird 0 0 0.00 3 3 0.04 0 0 0.00 3 3 0.02

Swainson’s hawk 0 0 0.00 3 3 0.04 0 0 0.00 3 3 0.02

great horned owl 2 2 0.04 1 1 0.01 0 0 0.00 3 3 0.02

turkey vulture 0 0 0.00 2 1 0.03 0 0 0.00 2 1 0.01

spotted towhee 0 0 0.00 1 1 0.01 1 1 0.08 2 2 0.01

killdeer 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

broad-tailed hummingbird 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

Brewer's blackbird 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

tree swallow 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

red-headed woodpecker 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

ruby-crowned kinglet 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

northern harrier 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

loggerhead shrike 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

grasshopper sparrow 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

golden eagle 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

great blue heron 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

dark-eyed junco 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

Bullock's oriole 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

bald eagle 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Grand Total 95 40 1.76 603 229 8.38 19 20 1.58 717 289 5.20

* Mean use=# birds/30 min.
Species

Summer 2010 Fall 2010

Table 2d. Avian species observed during 20-minute point count surveys at the off-site reference locations, 2010-2011.

Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

western meadowlark 68 67 1.66 112 50 1.62 2 1 0.06 182 118 1.27

horned lark 88 48 2.15 14 13 0.20 4 3 0.12 106 64 0.74

grasshopper sparrow 66 45 1.61 12 10 0.17 0 0 0.00 78 55 0.55

European starling 60 1 1.46 4 2 0.06 0 0 0.00 64 3 0.45

song sparrow 3 3 0.07 39 22 0.57 0 0 0.00 42 25 0.29

vesper sparrow 5 4 0.12 34 9 0.49 0 0 0.00 39 13 0.27

red-winged blackbird 20 20 0.49 9 8 0.13 0 0 0.00 29 28 0.20

black-billed magpie 0 0 0.00 20 17 0.29 1 1 0.03 21 18 0.15

western kingbird 11 11 0.27 9 7 0.13 0 0 0.00 20 18 0.14

American tree sparrow 0 0 0.00 11 7 0.16 6 2 0.18 17 9 0.12

American kestrel 8 6 0.20 8 5 0.12 0 0 0.00 16 11 0.11

mourning dove 7 5 0.17 8 6 0.12 0 0 0.00 15 11 0.10

lark bunting 1 1 0.02 12 2 0.17 0 0 0.00 13 3 0.09

American goldfinch 11 3 0.27 2 2 0.03 0 0 0.00 13 5 0.09

unidentified songbird 1 1 0.02 0 0 0.00 9 3 0.27 10 4 0.07

Say's phoebe 7 7 0.17 3 3 0.04 0 0 0.00 10 10 0.07

barn swallow 10 6 0.24 0 0 0.00 0 0 0.00 10 6 0.07

tree swallow 9 3 0.22 0 0 0.00 0 0 0.00 9 3 0.06

common raven 2 2 0.05 2 1 0.03 5 4 0.15 9 7 0.06

chipping sparrow 6 6 0.15 3 2 0.04 0 0 0.00 9 8 0.06

Brewer's blackbird 9 3 0.22 0 0 0.00 0 0 0.00 9 3 0.06

* Mean use=# birds/20 min.
Species

Summer 2010 Fall 2010

Table 2d. Avian species observed during 20-minute point count surveys at the off-site reference locations, 2010-2011.

Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Overall

 #

Birds

#

Obs.

Mean

Use*

unidentified sparrow 0 0 0.00 7 7 0.10 0 0 0.00 7 7 0.05

American crow 0 0 0.00 7 6 0.10 0 0 0.00 7 6 0.05

turkey vulture 0 0 0.00 5 4 0.07 0 0 0.00 5 4 0.03

red-tailed hawk 0 0 0.00 2 2 0.03 3 2 0.09 5 4 0.03

Brewer's sparrow 0 0 0.00 5 3 0.07 0 0 0.00 5 3 0.03

northern harrier 0 0 0.00 0 0 0.00 3 3 0.09 3 3 0.02

broad-tailed hummingbird 3 3 0.07 0 0 0.00 0 0 0.00 3 3 0.02

unidentified bird 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

lark sparrow 2 2 0.05 0 0 0.00 0 0 0.00 2 2 0.01

hairy woodpecker 0 0 0.00 2 1 0.03 0 0 0.00 2 1 0.01

savannah sparrow 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

northern flicker 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

greater scaup 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

gray catbird 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

black-capped chickadee 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Grand Total 399 249 9.73 335 194 4.86 33 19 1.00 767 462 5.36

* Mean use=# birds/20 min.
Table 3a. Avian mean use, by species group, observed during 30-minute point count surveys at the National Wind Technology Center, 2010.

Species

Species Group

Spring 2010 Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Winter 2010 Overall

Songbirds

western meadowlark 6 5 0.10 84 74 1.17 26 26 1.53 116 105 0.78

vesper sparrow 0 0 0.00 50 29 0.69 33 28 1.94 83 57 0.56

barn swallow 0 0 0.00 13 4 0.18 9 2 0.53 22 6 0.15

black-billed magpie 9 5 0.15 9 6 0.13 0 0 0.00 18 11 0.12

common raven 4 3 0.07 9 7 0.13 1 1 0.06 14 11 0.09

American robin 3 2 0.05 8 8 0.11 3 3 0.18 14 13 0.09

Brewer's blackbird 0 0 0.00 13 7 0.18 0 0 0.00 13 7 0.09

European starling 0 0 0.00 11 6 0.15 1 1 0.06 12 7 0.08

spotted towhee 0 0 0.00 6 5 0.08 3 3 0.18 9 8 0.06

mountain bluebird 8 1 0.13 0 0 0.00 0 0 0.00 8 1 0.05

western kingbird 0 0 0.00 2 1 0.03 4 3 0.24 6 4 0.04

red-winged blackbird 0 0 0.00 4 3 0.06 0 0 0.00 4 3 0.03

black-capped chickadee 4 1 0.07 0 0 0.00 0 0 0.00 4 1 0.03

Say's phoebe 0 0 0.00 2 2 0.03 1 1 0.06 3 3 0.02

horned lark 0 0 0.00 1 1 0.01 2 1 0.12 3 2 0.02

grasshopper sparrow 0 0 0.00 0 0 0.00 3 3 0.18 3 3 0.02

dark-eyed junco 1 1 0.02 2 1 0.03 0 0 0.00 3 2 0.02

American goldfinch 0 0 0.00 1 1 0.01 2 1 0.12 3 2 0.02

loggerhead shrike 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

house finch 0 0 0.00 0 0 0.00 1 1 0.06 1 1 0.01

common grackle 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

blue jay 0 0 0.00 0 0 0.00 1 1 0.06 1 1 0.01

brown-headed cowbird 0 0 0.00 0 0 0.00 1 1 0.06 1 1 0.01

Group Total 35 18 0.58 217 157 3.01 91 76 5.35 343 251 2.30

Raptors

red-tailed hawk 7 6 0.12 3 3 0.04 2 1 0.12 12 10 0.08

turkey vulture 0 0 0.00 7 3 0.10 3 3 0.18 10 6 0.07

* Mean use=# birds/30 min.
Table 3a. Avian mean use, by species group, observed during 30-minute point count surveys at the National Wind Technology Center, 2010.

Species

Species Group

Spring 2010 Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Winter 2010 Overall

American kestrel 3 3 0.05 6 6 0.08 0 0 0.00 9 9 0.06

rough-legged hawk 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

northern harrier 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

ferruginous hawk 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 11 10 0.18 18 14 0.25 5 4 0.29 34 28 0.23

Waterfowl

mallard 0 0 0.00 6 5 0.08 0 0 0.00 6 5 0.04

Group Total 0 0 0.00 6 5 0.08 0 0 0.00 6 5 0.04

Waterbirds

Wilson's snipe 0 0 0.00 1 1 0.01 3 2 0.18 4 3 0.03

killdeer 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 0 0 0.00 2 2 0.03 3 2 0.18 5 4 0.03

Woodpeckers

downy woodpecker 3 2 0.05 0 0 0.00 0 0 0.00 3 2 0.02

Group Total 3 2 0.05 0 0 0.00 0 0 0.00 3 2 0.02

Pigeons/Doves

Eurasian collared-dove 0 0 0.00 2 1 0.03 0 0 0.00 2 1 0.01

mourning dove 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 0 0 0.00 3 2 0.04 0 0 0.00 3 2 0.02

Swifts/Hummingbirds

broad-tailed hummingbird 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Grand Total 49 30 0.82 247 181 3.43 99 82 5.82 395 293 2.65

* Mean use=# birds/30 min.
Table 3b. Avian mean use, by species group, observed during 20-minute point count surveys at the National Wind Technology Center, 2010-2011.

Species

Species Group

Fall 2010 Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Summer 2010 Overall

Songbirds

western meadowlark 72 65 1.85 29 25 0.46 0 0 0.00 101 90 0.78

red-winged blackbird 99 11 2.54 0 0 0.00 0 0 0.00 99 11 0.76

horned lark 47 39 1.21 20 15 0.32 3 1 0.11 70 55 0.54

grasshopper sparrow 53 33 1.36 15 11 0.24 0 0 0.00 68 44 0.52

western kingbird 46 32 1.18 2 1 0.03 0 0 0.00 48 33 0.37

vesper sparrow 37 32 0.95 4 3 0.06 0 0 0.00 41 35 0.32

Brewer's blackbird 29 8 0.74 10 1 0.16 0 0 0.00 39 9 0.30

song sparrow 7 7 0.18 24 17 0.38 0 0 0.00 31 24 0.24

black-billed magpie 1 1 0.03 11 8 0.17 19 8 0.68 31 17 0.24

barn swallow 16 14 0.41 10 7 0.16 0 0 0.00 26 21 0.20

tree swallow 22 8 0.56 0 0 0.00 0 0 0.00 22 8 0.17

chipping sparrow 20 20 0.51 0 0 0.00 0 0 0.00 20 20 0.15

Say's phoebe 15 13 0.38 3 3 0.05 0 0 0.00 18 16 0.14

American goldfinch 3 3 0.08 11 8 0.17 0 0 0.00 14 11 0.11

common raven 6 5 0.15 0 0 0.00 7 7 0.25 13 12 0.10

unidentified sparrow 0 0 0.00 5 5 0.08 0 0 0.00 5 5 0.04

Brewer's sparrow 0 0 0.00 5 3 0.08 0 0 0.00 5 3 0.04

mountain chickadee 0 0 0.00 2 2 0.03 2 2 0.07 4 4 0.03

American tree sparrow 0 0 0.00 4 3 0.06 0 0 0.00 4 3 0.03

American crow 0 0 0.00 4 4 0.06 0 0 0.00 4 4 0.03

unidentified songbird 0 0 0.00 2 2 0.03 1 1 0.04 3 3 0.02

Townsend’s solitaire 3 1 0.08 0 0 0.00 0 0 0.00 3 1 0.02

loggerhead shrike 2 2 0.05 1 1 0.02 0 0 0.00 3 3 0.02

gray catbird 1 1 0.03 2 2 0.03 0 0 0.00 3 3 0.02

black-capped chickadee 3 3 0.08 0 0 0.00 0 0 0.00 3 3 0.02

European starling 2 2 0.05 0 0 0.00 0 0 0.00 2 2 0.02

dark-eyed junco 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.02

house finch 1 1 0.03 0 0 0.00 0 0 0.00 1 1 0.01

* Mean use=# birds/20 min.
Table 3b. Avian mean use, by species group, observed during 20-minute point count surveys at the National Wind Technology Center, 2010-2011. 

Species

Species Group

Fall 2010 Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Summer 2010 Overall

American robin 0 0 0.00 1 1 0.02 0 0 0.00 1 1 0.01

Group Total 485 301 12.44 167 124 2.65 32 19 1.14 684 444 5.26

Pigeons/Doves

mourning dove 11 11 0.28 14 8 0.22 0 0 0.00 25 19 0.19

Eurasian collared-dove 1 1 0.03 0 0 0.00 0 0 0.00 1 1 0.01

Group Total 12 12 0.31 14 8 0.22 0 0 0.00 26 20 0.20

Raptors

red-tailed hawk 1 1 0.03 4 3 0.06 1 1 0.04 6 5 0.05

American kestrel 0 0 0.00 3 3 0.05 1 1 0.04 4 4 0.03

sharp-shinned hawk 0 0 0.00 1 1 0.02 0 0 0.00 1 1 0.01

Group Total 1 1 0.03 8 7 0.13 2 2 0.07 11 10 0.08

Woodpeckers

northern flicker 0 0 0.00 4 4 0.06 1 1 0.04 5 5 0.04

downy woodpecker 0 0 0.00 5 3 0.08 0 0 0.00 5 3 0.04

Group Total 0 0 0.00 9 7 0.14 1 1 0.04 10 8 0.08

Other

unidentified bird 1 1 0.03 3 2 0.05 0 0 0.00 4 3 0.03

Group Total 1 1 0.03 3 2 0.05 0 0 0.00 4 3 0.03

Cranes/Rails

sandhill crane 0 0 0.00 4 1 0.06 0 0 0.00 4 1 0.03

Group Total 0 0 0.00 4 1 0.06 0 0 0.00 4 1 0.03

Swifts/Hummingbirds

broad-tailed hummingbird 3 3 0.08 0 0 0.00 0 0 0.00 3 3 0.02

Group Total 3 3 0.08 0 0 0.00 0 0 0.00 3 3 0.02

Grand Total 502 318 12.87 205 149 3.25 35 22 1.25 742 489 5.71

* Mean use=# birds/20 min.
Table 3c. Avian mean use, by species group, observed during 30-minute point count surveys at off-site reference locations, 2010.

Species

Species Group

Spring 2010 Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Winter 2010 Overall

Songbirds

red-winged blackbird 2 1 0.04 132 14 1.83 0 0 0.00 134 15 0.97

western meadowlark 1 1 0.02 121 79 1.68 9 9 0.75 131 89 0.95

horned lark 26 15 0.48 69 25 0.96 0 0 0.00 95 40 0.69

vesper sparrow 0 0 0.00 65 29 0.90 4 5 0.33 69 34 0.50

American pipit 0 0 0.00 23 3 0.32 0 0 0.00 23 3 0.17

American crow 0 0 0.00 21 4 0.29 0 0 0.00 21 4 0.15

black-billed magpie 13 5 0.24 7 5 0.10 0 0 0.00 20 10 0.14

mountain bluebird 6 1 0.11 12 2 0.17 0 0 0.00 18 3 0.13

common raven 10 7 0.19 6 4 0.08 1 1 0.08 17 12 0.12

cedar waxwing 0 0 0.00 16 2 0.22 0 0 0.00 16 2 0.12

European starling 3 1 0.06 12 4 0.17 0 0 0.00 15 5 0.11

American robin 0 0 0.00 12 7 0.17 0 0 0.00 12 7 0.09

barn swallow 0 0 0.00 11 4 0.15 0 0 0.00 11 4 0.08

common grackle 0 0 0.00 4 3 0.06 0 0 0.00 4 3 0.03

western kingbird 0 0 0.00 3 3 0.04 0 0 0.00 3 3 0.02

spotted towhee 0 0 0.00 1 1 0.01 1 1 0.08 2 2 0.01

Brewer's blackbird 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

tree swallow 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

ruby-crowned kinglet 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

loggerhead shrike 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

grasshopper sparrow 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

dark-eyed junco 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

Bullock's oriole 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 62 32 1.15 522 196 7.25 15 16 1.25 599 244 4.34

Gulls/Terns

Franklin’s gull 0 0 0.00 40 1 0.56 0 0 0.00 40 1 0.29

Group Total 0 0 0.00 40 1 0.56 0 0 0.00 40 1 0.29

* Mean use=# birds/30 min.
Table 3c. Avian mean use, by species group, observed during 30-minute point count surveys at off-site reference locations, 2010.

Species

Species Group

Spring 2010 Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Winter 2010 Overall

Waterfowl

Canada goose 25 1 0.46 4 4 0.06 0 0 0.00 29 5 0.21

mallard 0 0 0.00 5 4 0.07 0 0 0.00 5 4 0.04

Group Total 25 1 0.46 9 8 0.13 0 0 0.00 34 9 0.25

Raptors

red-tailed hawk 4 3 0.07 3 2 0.04 1 1 0.08 8 6 0.06

American kestrel 0 0 0.00 5 5 0.07 2 2 0.17 7 7 0.05

Swainson’s hawk 0 0 0.00 3 3 0.04 0 0 0.00 3 3 0.02

great horned owl 2 2 0.04 1 1 0.01 0 0 0.00 3 3 0.02

turkey vulture 0 0 0.00 2 1 0.03 0 0 0.00 2 1 0.01

northern harrier 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

golden eagle 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

bald eagle 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 8 7 0.15 15 13 0.21 3 3 0.25 26 23 0.19

Waterbirds

long-billed curlew 0 0 0.00 5 1 0.07 0 0 0.00 5 1 0.04

Wilson's snipe 0 0 0.00 3 2 0.04 0 0 0.00 3 2 0.02

killdeer 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

great blue heron 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 0 0 0.00 11 6 0.15 0 0 0.00 11 6 0.08

Pigeons/Doves

mourning dove 0 0 0.00 3 2 0.04 1 1 0.08 4 3 0.03

Group Total 0 0 0.00 3 2 0.04 1 1 0.08 4 3 0.03

Swifts/Hummingbirds

broad-tailed hummingbird 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

Group Total 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

* Mean use=# birds/30 min.
Table 3c. Avian mean use, by species group, observed during 30-minute point count surveys at off-site reference locations, 2010.

Species

Species Group

Spring 2010 Summer 2010

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Winter 2010 Overall

Woodpeckers

red-headed woodpecker 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Grand Total 95 40 1.76 603 229 8.38 19 20 1.58 717 289 5.20

* Mean use=# birds/30 min.
Table 3d. Avian mean use, by species group, observed during 20-minute point count surveys at off-site reference locations, 2010-2011.

Species

Species Group

Fall 2010 Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Summer 2010 Overall

Songbirds

western meadowlark 68 67 1.66 112 50 1.62 2 1 0.06 182 118 1.27

horned lark 88 48 2.15 14 13 0.20 4 3 0.12 106 64 0.74

grasshopper sparrow 66 45 1.61 12 10 0.17 0 0 0.00 78 55 0.55

European starling 60 1 1.46 4 2 0.06 0 0 0.00 64 3 0.45

song sparrow 3 3 0.07 39 22 0.57 0 0 0.00 42 25 0.29

vesper sparrow 5 4 0.12 34 9 0.49 0 0 0.00 39 13 0.27

red-winged blackbird 20 20 0.49 9 8 0.13 0 0 0.00 29 28 0.20

black-billed magpie 0 0 0.00 20 17 0.29 1 1 0.03 21 18 0.15

western kingbird 11 11 0.27 9 7 0.13 0 0 0.00 20 18 0.14

American tree sparrow 0 0 0.00 11 7 0.16 6 2 0.18 17 9 0.12

lark bunting 1 1 0.02 12 2 0.17 0 0 0.00 13 3 0.09

American goldfinch 11 3 0.27 2 2 0.03 0 0 0.00 13 5 0.09

unidentified songbird 1 1 0.02 0 0 0.00 9 3 0.27 10 4 0.07

Say's phoebe 7 7 0.17 3 3 0.04 0 0 0.00 10 10 0.07

barn swallow 10 6 0.24 0 0 0.00 0 0 0.00 10 6 0.07

tree swallow 9 3 0.22 0 0 0.00 0 0 0.00 9 3 0.06

common raven 2 2 0.05 2 1 0.03 5 4 0.15 9 7 0.06

chipping sparrow 6 6 0.15 3 2 0.04 0 0 0.00 9 8 0.06

Brewer's blackbird 9 3 0.22 0 0 0.00 0 0 0.00 9 3 0.06

unidentified sparrow 0 0 0.00 7 7 0.10 0 0 0.00 7 7 0.05

American crow 0 0 0.00 7 6 0.10 0 0 0.00 7 6 0.05

Brewer's sparrow 0 0 0.00 5 3 0.07 0 0 0.00 5 3 0.03

lark sparrow 2 2 0.05 0 0 0.00 0 0 0.00 2 2 0.01

savannah sparrow 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

gray catbird 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

black-capped chickadee 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 380 234 9.27 307 173 4.45 27 14 0.82 714 421 4.99

* Mean use=# birds/20 min.
Table 3d. Avian mean use, by species group, observed during 20-minute point count surveys at off-site reference locations, 2010-2011.

Species

Species Group

Fall 2010 Winter 2010-2011

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

 #

Birds

#

Obs.

Mean

Use*

Summer 2010 Overall

Raptors

American kestrel 8 6 0.20 8 5 0.12 0 0 0.00 16 11 0.11

turkey vulture 0 0 0.00 5 4 0.07 0 0 0.00 5 4 0.03

red-tailed hawk 0 0 0.00 2 2 0.03 3 2 0.09 5 4 0.03

northern harrier 0 0 0.00 0 0 0.00 3 3 0.09 3 3 0.02

Group Total 8 6 0.20 15 11 0.22 6 5 0.18 29 22 0.20

Pigeons/Doves

mourning dove 7 5 0.17 8 6 0.12 0 0 0.00 15 11 0.10

Group Total 7 5 0.17 8 6 0.12 0 0 0.00 15 11 0.10

Woodpeckers

hairy woodpecker 0 0 0.00 2 1 0.03 0 0 0.00 2 1 0.01

northern flicker 0 0 0.00 1 1 0.01 0 0 0.00 1 1 0.01

Group Total 0 0 0.00 3 2 0.04 0 0 0.00 3 2 0.02

Swifts/Hummingbirds

broad-tailed hummingbird 3 3 0.07 0 0 0.00 0 0 0.00 3 3 0.02

Group Total 3 3 0.07 0 0 0.00 0 0 0.00 3 3 0.02

Other

unidentified bird 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

Group Total 0 0 0.00 2 2 0.03 0 0 0.00 2 2 0.01

Waterfowl

greater scaup 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

Group Total 1 1 0.02 0 0 0.00 0 0 0.00 1 1 0.01

Grand Total 399 249 9.73 335 194 4.86 33 19 1.00 767 462 5.36

* Mean use=# birds/20 min.
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 4a. Avian species observed by point during Winter 2010 30-minute point count surveys at the National

 Wind Technology Center.

black-billed magpie 9 5 4 0 0 0 1 4

mountain bluebird 8 1 0 0 8 0 0 0

red-tailed hawk 7 6 0 4 0 2 1 0

western meadowlark 6 5 0 0 0 4 1 1

common raven 4 3 2 0 1 0 0 1

black-capped chickadee 4 1 4 0 0 0 0 0

downy woodpecker 3 2 3 0 0 0 0 0

American robin 3 2 3 0 0 0 0 0

American kestrel 3 3 0 0 0 0 3 0

rough-legged hawk 1 1 0 0 1 0 0 0

dark-eyed junco 1 1 1 0 0 0 0 0

Grand Total 49 30 17 4 10 6 6 6
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 4b. Avian species observed by point during Spring 2010 30-minute point count surveys at the National

 Wind Technology Center.

western meadowlark 84 74 12 9 15 16 17 15

vesper sparrow 50 29 4 7 14 9 5 11

Brewer's blackbird 13 7 0 3 3 2 5 0

barn swallow 13 4 10 1 0 0 0 2

European starling 11 6 1 3 2 1 4 0

common raven 9 7 0 3 2 1 1 2

black-billed magpie 9 6 2 0 0 0 3 4

American robin 8 8 5 1 0 0 0 2

turkey vulture 7 3 6 1 0 0 0 0

spotted towhee 6 5 3 0 0 0 0 3

mallard 6 5 0 3 0 0 1 2

American kestrel 6 6 2 2 0 2 0 0

red-winged blackbird 4 3 1 2 0 0 1 0

red-tailed hawk 3 3 1 2 0 0 0 0

western kingbird 2 1 0 0 0 2 0 0

Say's phoebe 2 2 0 1 0 0 0 1

Eurasian collared-dove 2 1 2 0 0 0 0 0

dark-eyed junco 2 1 2 0 0 0 0 0

Wilson's snipe 1 1 0 0 0 0 0 1

northern harrier 1 1 0 0 1 0 0 0

mourning dove 1 1 1 0 0 0 0 0

loggerhead shrike 1 1 0 0 0 0 1 0

killdeer 1 1 1 0 0 0 0 0

horned lark 1 1 0 1 0 0 0 0

ferruginous hawk 1 1 1 0 0 0 0 0

common grackle 1 1 1 0 0 0 0 0

broad-tailed hummingbird 1 1 0 0 0 0 1 0

American goldfinch 1 1 1 0 0 0 0 0

Grand Total 247 181 56 39 37 33 39 43
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 4c. Avian species observed by point during early Summer 2010 30-minute point count surveys at the National

 Wind Technology Center.

vesper sparrow 33 28 6 5 5 4 9 4

western meadowlark 26 26 4 3 2 8 6 3

barn swallow 9 2 1 0 8 0 0 0

western kingbird 4 3 0 0 0 3 0 1

Wilson's snipe 3 2 0 0 0 0 0 3

turkey vulture 3 3 1 0 0 2 0 0

spotted towhee 3 3 3 0 0 0 0 0

grasshopper sparrow 3 3 1 0 0 1 0 1

American robin 3 3 2 0 0 0 0 1

red-tailed hawk 2 1 0 2 0 0 0 0

horned lark 2 1 0 0 0 0 0 2

American goldfinch 2 1 0 0 0 0 0 2

Say's phoebe 1 1 1 0 0 0 0 0

house finch 1 1 0 0 0 1 0 0

European starling 1 1 0 0 1 0 0 0

common raven 1 1 0 0 0 0 0 1

blue jay 1 1 1 0 0 0 0 0

brown-headed cowbird 1 1 1 0 0 0 0 0

Grand Total 99 82 21 10 16 19 15 18
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Avian species observed by point during late Summer 2010 20-minute point count surveys at the National Wind

Technology Center.

Table 4d.

red-winged blackbird 99 11 0 95 0 0 1 3

western meadowlark 72 65 10 16 13 23 4 6

grasshopper sparrow 53 33 25 9 5 6 3 5

horned lark 47 39 2 7 12 11 9 6

western kingbird 46 32 7 13 3 15 4 4

vesper sparrow 37 32 10 7 9 3 3 5

Brewer's blackbird 29 8 3 25 0 0 1 0

tree swallow 22 8 3 2 1 0 16 0

chipping sparrow 20 20 4 3 7 3 0 3

barn swallow 16 14 5 3 5 0 1 2

Say's phoebe 15 13 9 4 0 1 0 1

mourning dove 11 11 1 1 1 3 2 3

song sparrow 7 7 0 0 5 1 1 0

common raven 6 5 3 1 0 1 0 1

Townsend’s solitaire 3 1 3 0 0 0 0 0

broad-tailed hummingbird 3 3 0 0 1 0 2 0

black-capped chickadee 3 3 0 1 0 0 2 0

American goldfinch 3 3 2 0 0 0 0 1

loggerhead shrike 2 2 0 0 0 0 2 0

European starling 2 2 0 2 0 0 0 0

unidentified bird 1 1 0 0 1 0 0 0

red-tailed hawk 1 1 0 1 0 0 0 0

house finch 1 1 0 0 0 0 1 0

gray catbird 1 1 1 0 0 0 0 0

Eurasian collared-dove 1 1 0 0 0 0 1 0

black-billed magpie 1 1 0 0 0 0 1 0

Grand Total 502 318 88 190 63 67 54 40
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Avian species observed by point during Fall 2010 20-minute point count surveys at the National Wind 

Technology Center.

Table 4e.

western meadowlark 29 25 4 6 1 9 3 6

song sparrow 24 17 4 15 0 4 1 0

horned lark 20 15 2 3 1 9 1 4

grasshopper sparrow 15 11 2 6 0 3 4 0

mourning dove 14 8 2 7 2 2 1 0

black-billed magpie 11 8 6 1 0 2 0 2

American goldfinch 11 8 4 0 0 3 0 4

Brewer's blackbird 10 1 0 10 0 0 0 0

barn swallow 10 7 5 2 3 0 0 0

unidentified sparrow 5 5 2 1 0 1 1 0

downy woodpecker 5 3 5 0 0 0 0 0

Brewer's sparrow 5 3 0 5 0 0 0 0

vesper sparrow 4 3 2 0 1 0 1 0

sandhill crane 4 1 0 0 0 0 0 4

red-tailed hawk 4 3 1 0 0 0 1 2

northern flicker 4 4 4 0 0 0 0 0

American tree sparrow 4 3 3 0 0 0 0 1

American crow 4 4 2 1 1 0 0 0

unidentified bird 3 2 2 0 0 0 0 1

Say's phoebe 3 3 3 0 0 0 0 0

American kestrel 3 3 0 0 1 2 0 0

western kingbird 2 1 0 0 0 0 2 0

unidentified songbird 2 2 1 0 1 0 0 0

mountain chickadee 2 2 2 0 0 0 0 0

gray catbird 2 2 2 0 0 0 0 0

dark-eyed junco 2 2 2 0 0 0 0 0

sharp-shinned hawk 1 1 1 0 0 0 0 0

loggerhead shrike 1 1 0 1 0 0 0 0

American robin 1 1 0 0 1 0 0 0

Grand Total 205 149 61 58 12 35 15 24
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Avian species observed by point during Winter 2010-2011 20-minute point count surveys at the National 

Wind Technology Center. 

Table 4f.

black-billed magpie 19 8 1 3 1 0 0 14

common raven 7 7 1 0 3 1 1 1

horned lark 3 1 0 3 0 0 0 0

mountain chickadee 2 2 2 0 0 0 0 0

unidentified songbird 1 1 0 0 0 0 0 1

red-tailed hawk 1 1 0 0 0 1 0 0

northern flicker 1 1 1 0 0 0 0 0

American kestrel 1 1 0 0 0 1 0 0

Grand Total 35 22 5 6 4 3 1 16
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 4g. Avian species observed by point during Winter 2010 30-minute point count surveys at off-site reference 

 locations.

horned lark 26 15 1 2 20 0 2 1

Canada goose 25 1 0 0 0 25 0 0

black-billed magpie 13 5 0 0 0 0 1 12

common raven 10 7 3 4 0 2 1 0

mountain bluebird 6 1 0 0 0 6 0 0

red-tailed hawk 4 3 3 0 0 0 0 1

European starling 3 1 0 0 0 0 0 3

red-winged blackbird 2 1 0 0 0 2 0 0

great horned owl 2 2 0 0 0 2 0 0

western meadowlark 1 1 0 0 0 0 0 1

northern harrier 1 1 0 0 0 1 0 0

golden eagle 1 1 0 0 0 0 1 0

dark-eyed junco 1 1 0 0 0 1 0 0

Grand Total 95 40 7 6 20 39 5 18
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 4h. Avian species observed by point during Spring 2010 30-minute point count surveys at off-site reference 

 locations.

red-winged blackbird 132 14 35 0 0 93 0 4

western meadowlark 121 79 24 20 19 23 17 18

horned lark 69 25 3 9 19 8 11 19

vesper sparrow 65 29 7 10 5 28 9 6

Franklin’s gull 40 1 0 0 40 0 0 0

American pipit 23 3 3 20 0 0 0 0

American crow 21 4 6 15 0 0 0 0

cedar waxwing 16 2 0 0 6 0 0 10

mountain bluebird 12 2 0 12 0 0 0 0

European starling 12 4 9 0 0 0 3 0

American robin 12 7 0 0 0 5 2 5

barn swallow 11 4 0 0 0 8 3 0

black-billed magpie 7 5 0 0 0 2 2 3

common raven 6 4 0 0 0 2 3 1

mallard 5 4 4 0 0 1 0 0

long-billed curlew 5 1 0 0 5 0 0 0

American kestrel 5 5 1 0 1 0 2 1

common grackle 4 3 0 3 0 0 1 0

Canada goose 4 4 2 0 0 2 0 0

Wilson's snipe 3 2 0 0 0 1 2 0

western kingbird 3 3 0 0 0 2 0 1

Swainson’s hawk 3 3 0 0 0 3 0 0

red-tailed hawk 3 2 2 0 0 0 1 0

mourning dove 3 2 0 0 0 3 0 0

turkey vulture 2 1 0 2 0 0 0 0

killdeer 2 2 1 0 0 1 0 0

broad-tailed hummingbird 2 2 0 0 0 0 1 1

Brewer's blackbird 2 2 0 2 0 0 0 0

tree swallow 1 1 0 0 0 0 1 0

spotted towhee 1 1 0 0 0 1 0 0

red-headed woodpecker 1 1 0 0 0 0 0 1

ruby-crowned kinglet 1 1 0 0 0 1 0 0

loggerhead shrike 1 1 0 0 0 0 1 0

grasshopper sparrow 1 1 0 0 0 0 1 0

great horned owl 1 1 0 0 0 1 0 0

great blue heron 1 1 0 0 0 1 0 0

Bullock's oriole 1 1 0 0 0 1 0 0

bald eagle 1 1 0 0 0 0 1 0

Grand Total 603 229 97 93 95 187 61 70
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 4i. Avian species observed by point during early Summer 2010 30-minute point count surveys at off-site 

 reference locations.

western meadowlark 9 9 3 1 2 0 1 2

vesper sparrow 4 5 0 1 1 0 1 1

American kestrel 2 2 0 0 0 2 0 0

spotted towhee 1 1 0 0 0 1 0 0

red-tailed hawk 1 1 0 0 0 1 0 0

mourning dove 1 1 0 0 0 0 0 1

common raven 1 1 1 0 0 0 0 0

Grand Total 19 20 4 2 3 4 2 4
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 4j. Avian species observed by point during late Summer 2010 20-minute point count surveys at off-site reference locations.

horned lark 88 48 13 19 11 4 36 5

western meadowlark 68 67 11 20 20 8 3 6

grasshopper sparrow 66 45 18 12 15 12 2 7

European starling 60 1 0 0 60 0 0 0

red-winged blackbird 20 20 4 4 1 4 5 2

western kingbird 11 11 6 0 4 0 1 0

American goldfinch 11 3 0 0 0 3 5 3

barn swallow 10 6 3 2 0 2 1 2

tree swallow 9 3 6 0 0 1 0 2

Brewer's blackbird 9 3 3 4 2 0 0 0

American kestrel 8 6 0 7 0 0 1 0

Say's phoebe 7 7 3 0 1 0 2 1

mourning dove 7 5 0 5 0 2 0 0

chipping sparrow 6 6 2 0 0 1 2 1

vesper sparrow 5 4 0 3 2 0 0 0

song sparrow 3 3 0 0 0 2 1 0

broad-tailed hummingbird 3 3 1 0 0 0 1 1

lark sparrow 2 2 2 0 0 0 0 0

common raven 2 2 0 0 1 0 1 0

unidentified songbird 1 1 1 0 0 0 0 0

savannah sparrow 1 1 0 1 0 0 0 0

lark bunting 1 1 0 0 0 0 1 0

greater scaup 1 1 0 1 0 0 0 0

Grand Total 399 249 73 78 117 39 62 30
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 4k. Avian species observed by point during Fall 2010 20-minute point count surveys at off-site

 reference locations.

western meadowlark 112 50 21 58 11 5 8 9

song sparrow 39 22 2 6 13 3 5 10

vesper sparrow 34 9 1 2 0 3 26 2

black-billed magpie 20 17 9 2 0 7 0 2

horned lark 14 13 0 4 4 1 5 0

lark bunting 12 2 0 0 12 0 0 0

grasshopper sparrow 12 10 0 0 7 1 2 2

American tree sparrow 11 7 0 0 5 3 2 1

western kingbird 9 7 0 0 2 1 4 2

red-winged blackbird 9 8 2 0 0 0 3 4

mourning dove 8 6 1 3 0 1 3 0

American kestrel 8 5 1 5 2 0 0 0

unidentified sparrow 7 7 2 2 2 1 0 0

American crow 7 6 1 1 2 0 2 1

turkey vulture 5 4 1 0 4 0 0 0

Brewer's sparrow 5 3 0 0 3 0 1 1

European starling 4 2 0 0 4 0 0 0

Say's phoebe 3 3 0 0 0 2 1 0

chipping sparrow 3 2 0 1 0 2 0 0

unidentified bird 2 2 0 0 1 0 0 1

red-tailed hawk 2 2 0 1 0 0 1 0

hairy woodpecker 2 1 0 0 0 0 2 0

common raven 2 1 0 0 2 0 0 0

American goldfinch 2 2 0 1 0 1 0 0

northern flicker 1 1 0 0 1 0 0 0

gray catbird 1 1 0 0 0 1 0 0

black-capped chickadee 1 1 0 0 0 1 0 0

Grand Total 335 194 41 86 75 33 65 35
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Avian species observed by point during Winter 2010-2011 20-minute point count surveys at 

off-site reference locations.

Table 4l.

unidentified songbird 9 3 0 1 0 0 0 8

American tree sparrow 6 2 0 0 0 1 0 5

common raven 5 4 1 1 2 0 0 1

horned lark 4 3 0 0 0 1 1 2

red-tailed hawk 3 2 1 0 0 2 0 0

northern harrier 3 3 0 0 1 0 1 1

western meadowlark 2 1 0 0 0 0 0 2

black-billed magpie 1 1 0 0 0 1 0 0

Grand Total 33 19 2 2 3 5 2 19
Table 5a. .

Observations

# %

Individuals

# %

Winter 2010

Observations

# %

Individuals

#

Spring 2010

%

Observations

# %

Individuals

# %

Summer 2010

Observations

# %

Individuals

# %

Overall

Summary of avian flight heights (includes flying birds only) in relation to the 1.5-MW turbine rotor-swept area (RSA) during 30-minute point count 

 surveys at the National Wind Technology Center, 2010.

Non-raptors

At RSA height (41.5m–118.5m) 2 33.3% 3 33.3% 1 2.6% 1 1.8% 0 0.0% 0 0.0% 3 6.1% 4 5.6%

Below RSA height (<41.5m) 4 66.7% 6 66.7% 37 97.4% 56 98.2% 5 100.0% 6 100.0% 46 93.9% 68 94.4%

Raptors

At RSA height (41.5m–118.5m) 0 0.0% 0 0.0% 3 37.5% 5 41.7% 0 0.0% 0 0.0% 3 21.4% 5 27.8%

Below RSA height (<41.5m) 3 100.0% 3 100.0% 5 62.5% 7 58.3% 3 100.0% 3 100.0% 11 78.6% 13 72.2%
Table 5b. Summary of avian flight heights (includes flying birds only) in relation to the 1.5-MW turbine rotor-swept area (RSA) during 20-minute point count

 surveys at the National Wind Technology Center, 2010-2011.

Observations

# %

Individuals

# %

Summer 2010

Observations

# %

Individuals

#

Fall 2010

%

Observations

# %

Individuals

# %

Winter 2010-2011

Observations

# %

Individuals

# %

Overall

Non-raptors

At RSA height (41.5m–118.5m) 2 1.6% 3 1.0% 1 1.6% 4 3.6% 1 6.7% 1 3.6% 4 1.9% 8 1.8%

Below RSA height (<41.5m) 126 98.4% 291 99.0% 62 98.4% 107 96.4% 14 93.3% 27 96.4% 202 98.1% 425 98.2%

Raptors

At RSA height (41.5m–118.5m) 0 - 0 - 1 20.0% 1 16.7% 0 0.0% 0 0.0% 1 14.3% 1 12.5%

Below RSA height (<41.5m) 0 - 0 - 4 80.0% 5 83.3% 2 100.0% 2 100.0% 6 85.7% 7 87.5%
Table 5c. .

Observations

# %

Individuals

# %

Winter 2010

Observations

# %

Individuals

#

Spring 2010

%

Observations

# %

Individuals

# %

Summer 2010

Observations

# %

Individuals

# %

Overall

Summary of avian flight heights (includes flying birds only) in relation to the 2.3-MW turbine rotor-swept area (RSA) during 30-minute point count 

surveys at the National Wind Technology Center, 2010.

Non-raptors

At RSA height (29.5m–130.5m) 2 33.3% 3 33.3% 2 5.3% 8 14.0% 0 0.0% 0 0.0% 4 8.2% 11 15.3%

Below RSA height (<29.5m) 4 66.7% 6 66.7% 36 94.7% 49 86.0% 5 100.0% 6 100.0% 45 91.8% 61 84.7%

Raptors

At RSA height (29.5m–130.5m) 0 0.0% 0 0.0% 4 50.0% 8 66.7% 0 0.0% 0 0.0% 4 28.6% 8 44.4%

Below RSA height (<29.5m) 3 100.0% 3 100.0% 4 50.0% 4 33.3% 3 100.0% 3 100.0% 10 71.4% 10 55.6%
Table 5d. 

Observations

# %

Individuals

# %

Summer 2010

Observations

# %

Individuals

#

Fall 2010

%

Observations

# %

Individuals

# %

Winter 2010-2011

Observations

# %

Individuals

# %

Overall

Summary of avian flight heights (includes flying birds only) in relation to the 2.3-MW turbine rotor-swept area (RSA) during 20-minute point count surveys at

the National Wind Technology Center, 2010-2011.

Non-raptors

At RSA height (29.5m–130.5m) 3 2.3% 6 2.0% 4 6.3% 10 9.0% 2 13.3% 2 7.1% 9 4.4% 18 4.2%

Below RSA height (<29.5m) 125 97.7% 288 98.0% 59 93.7% 101 91.0% 13 86.7% 26 92.9% 197 95.6% 415 95.8%

Raptors

At RSA height (29.5m–130.5m) 0 - 0 - 2 40.0% 2 33.3% 0 0.0% 0 0.0% 2 28.6% 2 25.0%

Below RSA height (<29.5m) 0 - 0 - 3 60.0% 4 66.7% 2 100.0% 2 100.0% 5 71.4% 6 75.0%
Table 5e. .

Observations

# %

Individuals

# %

Winter 2010

Observations

# %

Individuals

#

Spring 2010

%

Observations

# %

Individuals

# %

Summer 2010

Observations

# %

Individuals

# %

Overall

Summary of avian flight heights (includes flying birds only) in relation to the 3.0-MW turbine rotor-swept area (RSA) during 30-minute point count 

 surveys at the National Wind Technology Center, 2010.

Non-raptors

At RSA height (40m–140m) 2 33.3% 3 33.3% 1 2.6% 1 1.8% 0 0.0% 0 0.0% 3 6.1% 4 5.6%

Below RSA height (<40m) 4 66.7% 6 66.7% 37 97.4% 56 98.2% 5 100.0% 6 100.0% 46 93.9% 68 94.4%

Raptors

At RSA height (40m–140m) 0 0.0% 0 0.0% 3 37.5% 5 41.7% 0 0.0% 0 0.0% 3 21.4% 5 27.8%

Below RSA height (<40m) 3 100.0% 3 100.0% 5 62.5% 7 58.3% 3 100.0% 3 100.0% 11 78.6% 13 72.2%
Table 5f.

Observations

# %

Individuals

# %

Summer 2010

Observations

# %

Individuals

#

Fall 2010

%

Observations

# %

Individuals

# %

Winter 2010-2011

Observations

# %

Individuals

# %

Overall

Summary of avian flight heights (includes flying birds only) in relation to the 3.0-MW turbine rotor-swept area (RSA) during 20-minute point count surveys at the 

National Wind Technology Center, 2010-2011.

Non-raptors

At RSA height (40m–140m) 3 2.3% 6 2.0% 3 4.8% 9 8.1% 1 6.7% 1 3.6% 7 3.4% 16 3.7%

Below RSA height (<40m) 125 97.7% 288 98.0% 60 95.2% 102 91.9% 14 93.3% 27 96.4% 199 96.6% 417 96.3%

Raptors

At RSA height (40m–140m) 0 - 0 - 1 20.0% 1 16.7% 0 0.0% 0 0.0% 1 14.3% 1 12.5%

Below RSA height (<40m) 0 - 0 - 4 80.0% 5 83.3% 2 100.0% 2 100.0% 6 85.7% 7 87.5%
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 1.5-MW turbine rotor-swept area (RSA) 1 during Winter 2010 30-minute point count 

surveys at the National Wind Technology Center.

Table 6a.

common raven 0.05 0.07 (0.00 - 0.14) 100.0 0.0 75.0 25.0

western meadowlark 0.00 0.10 (0.01 - 0.19) 0.0 0.0 0.0 0.0

red-tailed hawk 0.00 0.12 (0.03 - 0.21) 14.3 0.0 0.0 100.0

rough-legged hawk 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

mountain bluebird 0.00 0.13 (0.00 - 0.35) 0.0 0.0 0.0 0.0

downy woodpecker 0.00 0.05 (0.00 - 0.11) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.02 (0.00 - 0.05) 0.0 0.0 0.0 0.0

black-capped chickadee 0.00 0.07 (0.00 - 0.18) 0.0 0.0 0.0 0.0

black-billed magpie 0.00 0.15 (0.03 - 0.27) 55.6 0.0 0.0 100.0

American robin 0.00 0.05 (0.00 - 0.13) 0.0 0.0 0.0 0.0

American kestrel 0.00 0.05 (0.00 - 0.10) 33.3 0.0 0.0 100.0

1

These values assume a rotor diameter of 77 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 1.5-MW turbine rotor-swept area 1 (RSA) during Spring 2010 30-minute point count surveys at the 

National Wind Technology Center.

Table 6b.

turkey vulture 0.04 0.10 (0.00 - 0.20) 100.0 0.0 42.9 57.1

red-tailed hawk 0.01 0.04 (0.00 - 0.08) 66.7 0.0 50.0 50.0

common raven 0.01 0.12 (0.04 - 0.20) 100.0 0.0 11.1 88.9

ferruginous hawk 0.01 0.01 (0.00 - 0.03) 100.0 0.0 100.0 0.0

Wilson's snipe 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

western meadowlark 0.00 1.18 (0.96 - 1.40) 4.7 0.0 0.0 100.0

western kingbird 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

vesper sparrow 0.00 0.68 (0.39 - 0.97) 0.0 0.0 0.0 0.0

spotted towhee 0.00 0.08 (0.01 - 0.15) 0.0 0.0 0.0 0.0

Say's phoebe 0.00 0.03 (0.00 - 0.06) 0.0 0.0 0.0 0.0

red-winged blackbird 0.00 0.05 (0.00 - 0.10) 100.0 0.0 0.0 100.0

northern harrier 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

mourning dove 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

mallard 0.00 0.08 (0.00 - 0.16) 100.0 0.0 0.0 100.0

loggerhead shrike 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

killdeer 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

horned lark 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

European starling 0.00 0.15 (0.04 - 0.26) 54.5 0.0 0.0 100.0

Eurasian collared-dove 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

common grackle 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

broad-tailed hummingbird 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

Brewer's blackbird 0.00 0.18 (0.05 - 0.31) 76.9 0.0 0.0 100.0

black-billed magpie 0.00 0.12 (0.04 - 0.20) 22.2 0.0 0.0 100.0

barn swallow 0.00 0.18 (0.00 - 0.36) 69.2 0.0 0.0 100.0

American robin 0.00 0.11 (0.05 - 0.17) 37.5 0.0 0.0 100.0

American kestrel 0.00 0.08 (0.02 - 0.14) 33.3 0.0 0.0 100.0

American goldfinch 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 77 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 1.5-MW turbine rotor-swept area (RSA) 1 during early Summer 2010 30-minute point count 

surveys at the National Wind Technology Center.

Table 6c.

Wilson's snipe 0.00 0.18 (0.00 - 0.39) 0.0 0.0 0.0 0.0

western meadowlark 0.00 1.53 (1.00 - 2.06) 3.8 0.0 0.0 100.0

western kingbird 0.00 0.24 (0.02 - 0.46) 50.0 0.0 0.0 100.0

vesper sparrow 0.00 1.94 (1.26 - 2.62) 3.0 0.0 0.0 100.0

turkey vulture 0.00 0.18 (0.02 - 0.34) 100.0 0.0 0.0 100.0

spotted towhee 0.00 0.18 (0.00 - 0.47) 0.0 0.0 0.0 0.0

Say's phoebe 0.00 0.06 (0.00 - 0.16) 100.0 0.0 0.0 100.0

red-tailed hawk 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

horned lark 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

house finch 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

grasshopper sparrow 0.00 0.18 (0.02 - 0.34) 0.0 0.0 0.0 0.0

European starling 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

common raven 0.00 0.06 (0.00 - 0.16) 100.0 0.0 0.0 100.0

blue jay 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

brown-headed cowbird 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

barn swallow 0.00 0.53 (0.00 - 1.30) 0.0 0.0 0.0 0.0

American robin 0.00 0.18 (0.02 - 0.34) 0.0 0.0 0.0 0.0

American goldfinch 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

1

These values assume a rotor diameter of 77 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 1.5-MW turbine rotor-swept area (RSA) 1 during late Summer 2010 20-minute point count surveys 

at the National Wind Technology Center.

Table 6d.

common raven 0.05 0.15 (0.04 - 0.26) 33.3 0.0 100.0 0.0

grasshopper sparrow 0.03 1.36 (0.35 - 2.37) 54.7 0.0 3.4 96.6

western meadowlark 0.00 1.85 (1.30 - 2.40) 27.8 0.0 0.0 100.0

western kingbird 0.00 1.18 (0.55 - 1.81) 37.0 0.0 0.0 100.0

vesper sparrow 0.00 0.95 (0.11 - 1.79) 35.1 0.0 0.0 100.0

unidentified bird 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

tree swallow 0.00 0.56 (0.00 - 1.20) 100.0 0.0 0.0 100.0

Townsend’s solitaire 0.00 0.08 (0.00 - 0.21) 0.0 0.0 0.0 0.0

song sparrow 0.00 0.18 (0.02 - 0.34) 14.3 0.0 0.0 100.0

Say's phoebe 0.00 0.38 (0.14 - 0.62) 66.7 0.0 0.0 100.0

red-winged blackbird 0.00 2.54 (0.00 - 6.76) 94.9 0.0 0.0 100.0

red-tailed hawk 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

mourning dove 0.00 0.28 (0.10 - 0.46) 54.5 0.0 0.0 100.0

loggerhead shrike 0.00 0.05 (0.00 - 0.13) 50.0 0.0 0.0 100.0

horned lark 0.00 1.21 (0.82 - 1.60) 46.8 0.0 0.0 100.0

house finch 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

gray catbird 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

European starling 0.00 0.05 (0.00 - 0.13) 0.0 0.0 0.0 0.0

Eurasian collared-dove 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

chipping sparrow 0.00 0.51 (0.28 - 0.74) 30.0 0.0 0.0 100.0

broad-tailed hummingbird 0.00 0.08 (0.01 - 0.15) 66.7 0.0 0.0 100.0

Brewer's blackbird 0.00 0.74 (0.00 - 1.68) 89.7 0.0 0.0 100.0

black-capped chickadee 0.00 0.08 (0.00 - 0.17) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

barn swallow 0.00 0.41 (0.12 - 0.70) 93.8 0.0 0.0 100.0

American goldfinch 0.00 0.08 (0.01 - 0.15) 66.7 0.0 0.0 100.0

1

These values assume a rotor diameter of 77 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 1.5-MW turbine rotor-swept area (RSA) 1 during Fall 2010 20-minute point count surveys at the

National Wind Technology Center.

Table 6e.

sandhill crane 0.06 0.06 (0.00 - 0.16) 100.0 0.0 100.0 0.0

red-tailed hawk 0.01 0.06 (0.00 - 0.12) 75.0 0.0 33.3 66.7

western meadowlark 0.00 0.46 (0.17 - 0.75) 20.7 0.0 0.0 100.0

western kingbird 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

vesper sparrow 0.00 0.06 (0.00 - 0.12) 75.0 0.0 0.0 100.0

unidentified sparrow 0.00 0.08 (0.01 - 0.15) 0.0 0.0 0.0 0.0

unidentified songbird 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

unidentified bird 0.00 0.05 (0.00 - 0.11) 33.3 0.0 0.0 100.0

sharp-shinned hawk 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

song sparrow 0.00 0.38 (0.09 - 0.67) 58.3 0.0 0.0 100.0

Say's phoebe 0.00 0.05 (0.00 - 0.11) 33.3 0.0 0.0 100.0

northern flicker 0.00 0.06 (0.00 - 0.12) 75.0 0.0 0.0 100.0

mourning dove 0.00 0.22 (0.08 - 0.36) 85.7 0.0 0.0 100.0

mountain chickadee 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

loggerhead shrike 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

horned lark 0.00 0.32 (0.13 - 0.51) 65.0 0.0 0.0 100.0

grasshopper sparrow 0.00 0.24 (0.08 - 0.40) 40.0 0.0 0.0 100.0

gray catbird 0.00 0.03 (0.00 - 0.07) 50.0 0.0 0.0 100.0

downy woodpecker 0.00 0.08 (0.00 - 0.19) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

Brewer's sparrow 0.00 0.08 (0.00 - 0.19) 60.0 0.0 0.0 100.0

Brewer's blackbird 0.00 0.16 (0.00 - 0.42) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.17 (0.06 - 0.28) 81.8 0.0 0.0 100.0

barn swallow 0.00 0.16 (0.00 - 0.32) 100.0 0.0 0.0 100.0

American tree sparrow 0.00 0.06 (0.00 - 0.12) 50.0 0.0 0.0 100.0

American robin 0.00 0.02 (0.00 - 0.05) 0.0 0.0 0.0 0.0

American kestrel 0.00 0.05 (0.01 - 0.09) 66.7 0.0 0.0 100.0

American goldfinch 0.00 0.17 (0.04 - 0.30) 72.7 0.0 0.0 100.0

American crow 0.00 0.06 (0.01 - 0.11) 50.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 77 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 1.5-MW turbine rotor-swept area (RSA) 1 during Winter 2010-2011 20-minute point count surveys 

at the National Wind Technology Center.

Table 6f.

common raven 0.04 0.25 (0.09 - 0.41) 71.4 0.0 20.0 80.0

unidentified songbird 0.00 0.04 (0.00 - 0.10) 0.0 0.0 0.0 0.0

red-tailed hawk 0.00 0.04 (0.00 - 0.10) 100.0 0.0 0.0 100.0

northern flicker 0.00 0.04 (0.00 - 0.10) 0.0 0.0 0.0 0.0

mountain chickadee 0.00 0.07 (0.00 - 0.15) 100.0 0.0 0.0 100.0

horned lark 0.00 0.11 (0.00 - 0.29) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.68 (0.09 - 1.27) 94.7 0.0 0.0 100.0

American kestrel 0.00 0.04 (0.00 - 0.10) 100.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 77 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 2.3-MW turbine rotor-swept area 1 (RSA) during Winter 2010 30-minute point count surveys 

at the National Wind Technology Center.

Table 6g.

common raven 0.05 0.07 (0.00 - 0.14) 100.0 0.0 75.0 25.0

western meadowlark 0.00 0.10 (0.01 - 0.19) 0.0 0.0 0.0 0.0

red-tailed hawk 0.00 0.12 (0.03 - 0.21) 14.3 0.0 0.0 100.0

rough-legged hawk 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

mountain bluebird 0.00 0.13 (0.00 - 0.35) 0.0 0.0 0.0 0.0

downy woodpecker 0.00 0.05 (0.00 - 0.11) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.02 (0.00 - 0.05) 0.0 0.0 0.0 0.0

black-capped chickadee 0.00 0.07 (0.00 - 0.18) 0.0 0.0 0.0 0.0

black-billed magpie 0.00 0.15 (0.03 - 0.27) 55.6 0.0 0.0 100.0

American robin 0.00 0.05 (0.00 - 0.13) 0.0 0.0 0.0 0.0

American kestrel 0.00 0.05 (0.00 - 0.10) 33.3 0.0 0.0 100.0

1

These values assume a rotor diameter of 101 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 2.3-MW turbine rotor-swept area 1 (RSA) during Spring 2010 30-minute point count surveys at 

the National Wind Technology Center.

Table 6h.

barn swallow 0.10 0.18 (0.00 - 0.36) 69.2 0.0 77.8 22.2

turkey vulture 0.09 0.10 (0.00 - 0.20) 100.0 0.0 85.7 14.3

common raven 0.01 0.13 (0.05 - 0.21) 100.0 0.0 11.1 88.9

red-tailed hawk 0.01 0.04 (0.00 - 0.08) 66.7 0.0 50.0 50.0

ferruginous hawk 0.01 0.01 (0.00 - 0.03) 100.0 0.0 100.0 0.0

Wilson's snipe 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

western meadowlark 0.00 1.17 (0.95 - 1.39) 4.8 0.0 0.0 100.0

western kingbird 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

vesper sparrow 0.00 0.69 (0.39 - 0.99) 0.0 0.0 0.0 0.0

spotted towhee 0.00 0.08 (0.01 - 0.15) 0.0 0.0 0.0 0.0

Say's phoebe 0.00 0.03 (0.00 - 0.06) 0.0 0.0 0.0 0.0

red-winged blackbird 0.00 0.06 (0.00 - 0.12) 100.0 0.0 0.0 100.0

northern harrier 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

mourning dove 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

mallard 0.00 0.08 (0.00 - 0.16) 100.0 0.0 0.0 100.0

loggerhead shrike 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

killdeer 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

horned lark 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

European starling 0.00 0.15 (0.04 - 0.26) 54.5 0.0 0.0 100.0

Eurasian collared-dove 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

common grackle 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

broad-tailed hummingbird 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

Brewer's blackbird 0.00 0.18 (0.05 - 0.31) 76.9 0.0 0.0 100.0

black-billed magpie 0.00 0.13 (0.04 - 0.22) 22.2 0.0 0.0 100.0

American robin 0.00 0.11 (0.05 - 0.17) 37.5 0.0 0.0 100.0

American kestrel 0.00 0.08 (0.02 - 0.14) 33.3 0.0 0.0 100.0

American goldfinch 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 101 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 2.3-MW turbine rotor-swept area (RSA) 1 during early Summer 2010 30-minute point count 

surveys at the National Wind Technology Center.

Table 6i.

Wilson's snipe 0.00 0.18 (0.00 - 0.39) 0.0 0.0 0.0 0.0

western meadowlark 0.00 1.53 (1.00 - 2.06) 3.8 0.0 0.0 100.0

western kingbird 0.00 0.24 (0.02 - 0.46) 50.0 0.0 0.0 100.0

vesper sparrow 0.00 1.94 (1.26 - 2.62) 3.0 0.0 0.0 100.0

turkey vulture 0.00 0.18 (0.02 - 0.34) 100.0 0.0 0.0 100.0

spotted towhee 0.00 0.18 (0.00 - 0.47) 0.0 0.0 0.0 0.0

Say's phoebe 0.00 0.06 (0.00 - 0.16) 100.0 0.0 0.0 100.0

red-tailed hawk 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

horned lark 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

house finch 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

grasshopper sparrow 0.00 0.18 (0.02 - 0.34) 0.0 0.0 0.0 0.0

European starling 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

common raven 0.00 0.06 (0.00 - 0.16) 100.0 0.0 0.0 100.0

blue jay 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

brown-headed cowbird 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

barn swallow 0.00 0.53 (0.00 - 1.30) 0.0 0.0 0.0 0.0

American robin 0.00 0.18 (0.02 - 0.34) 0.0 0.0 0.0 0.0

American goldfinch 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

1

These values assume a rotor diameter of 80 (m) and a hub height of 101 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 2.3-MW turbine rotor-swept area (RSA) 1 during late Summer 2010 20-minute point count surveys 

at the National Wind Technology Center.

Table 6j.

horned lark 0.08 1.21 (0.82 - 1.60) 46.8 0.0 13.6 86.4

common raven 0.05 0.15 (0.04 - 0.26) 33.3 0.0 100.0 0.0

grasshopper sparrow 0.03 1.36 (0.35 - 2.37) 54.7 0.0 3.4 96.6

western meadowlark 0.00 1.85 (1.30 - 2.40) 27.8 0.0 0.0 100.0

western kingbird 0.00 1.18 (0.55 - 1.81) 37.0 0.0 0.0 100.0

vesper sparrow 0.00 0.95 (0.11 - 1.79) 35.1 0.0 0.0 100.0

unidentified bird 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

tree swallow 0.00 0.56 (0.00 - 1.20) 100.0 0.0 0.0 100.0

Townsend’s solitaire 0.00 0.08 (0.00 - 0.21) 0.0 0.0 0.0 0.0

song sparrow 0.00 0.18 (0.02 - 0.34) 14.3 0.0 0.0 100.0

Say's phoebe 0.00 0.38 (0.14 - 0.62) 66.7 0.0 0.0 100.0

red-winged blackbird 0.00 2.54 (0.00 - 6.76) 94.9 0.0 0.0 100.0

red-tailed hawk 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

mourning dove 0.00 0.28 (0.10 - 0.46) 54.5 0.0 0.0 100.0

loggerhead shrike 0.00 0.05 (0.00 - 0.13) 50.0 0.0 0.0 100.0

house finch 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

gray catbird 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

European starling 0.00 0.05 (0.00 - 0.13) 0.0 0.0 0.0 0.0

Eurasian collared-dove 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

chipping sparrow 0.00 0.51 (0.28 - 0.74) 30.0 0.0 0.0 100.0

broad-tailed hummingbird 0.00 0.08 (0.01 - 0.15) 66.7 0.0 0.0 100.0

Brewer's blackbird 0.00 0.74 (0.00 - 1.68) 89.7 0.0 0.0 100.0

black-capped chickadee 0.00 0.08 (0.00 - 0.17) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

barn swallow 0.00 0.41 (0.12 - 0.70) 93.8 0.0 0.0 100.0

American goldfinch 0.00 0.08 (0.01 - 0.15) 66.7 0.0 0.0 100.0

1

These values assume a rotor diameter of 101 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 2.3-MW turbine rotor-swept area (RSA) 1 during Fall 2010 20-minute point count surveys

at the National Wind Technology Center.

Table 6k.

song sparrow 0.06 0.38 (0.09 - 0.67) 58.3 0.0 28.6 71.4

sandhill crane 0.06 0.06 (0.00 - 0.16) 100.0 0.0 100.0 0.0

mourning dove 0.03 0.22 (0.08 - 0.36) 85.7 0.0 16.7 83.3

American kestrel 0.02 0.05 (0.01 - 0.09) 66.7 0.0 50.0 50.0

red-tailed hawk 0.01 0.06 (0.00 - 0.12) 75.0 0.0 33.3 66.7

western meadowlark 0.00 0.46 (0.17 - 0.75) 20.7 0.0 0.0 100.0

western kingbird 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

vesper sparrow 0.00 0.06 (0.00 - 0.12) 75.0 0.0 0.0 100.0

unidentified sparrow 0.00 0.08 (0.01 - 0.15) 0.0 0.0 0.0 0.0

unidentified songbird 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

unidentified bird 0.00 0.05 (0.00 - 0.11) 33.3 0.0 0.0 100.0

sharp-shinned hawk 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

Say's phoebe 0.00 0.05 (0.00 - 0.11) 33.3 0.0 0.0 100.0

northern flicker 0.00 0.06 (0.00 - 0.12) 75.0 0.0 0.0 100.0

mountain chickadee 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

loggerhead shrike 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

horned lark 0.00 0.32 (0.13 - 0.51) 65.0 0.0 0.0 100.0

grasshopper sparrow 0.00 0.24 (0.08 - 0.40) 40.0 0.0 0.0 100.0

gray catbird 0.00 0.03 (0.00 - 0.07) 50.0 0.0 0.0 100.0

downy woodpecker 0.00 0.08 (0.00 - 0.19) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

Brewer's sparrow 0.00 0.08 (0.00 - 0.19) 60.0 0.0 0.0 100.0

Brewer's blackbird 0.00 0.16 (0.00 - 0.42) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.17 (0.06 - 0.28) 81.8 0.0 0.0 100.0

barn swallow 0.00 0.16 (0.00 - 0.32) 100.0 0.0 0.0 100.0

American tree sparrow 0.00 0.06 (0.00 - 0.12) 50.0 0.0 0.0 100.0

American robin 0.00 0.02 (0.00 - 0.05) 0.0 0.0 0.0 0.0

American goldfinch 0.00 0.17 (0.04 - 0.30) 72.7 0.0 0.0 100.0

American crow 0.00 0.06 (0.01 - 0.11) 50.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 101 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 2.3-MW turbine rotor-swept area (RSA) 1 during Winter 2010-2011 20-minute point count surveys at

the National Wind Technology Center.

Table 6l.

black-billed magpie 0.04 0.68 (0.09 - 1.27) 94.7 0.0 5.6 94.4

common raven 0.04 0.25 (0.09 - 0.41) 71.4 0.0 20.0 80.0

unidentified songbird 0.00 0.04 (0.00 - 0.10) 0.0 0.0 0.0 0.0

red-tailed hawk 0.00 0.04 (0.00 - 0.10) 100.0 0.0 0.0 100.0

northern flicker 0.00 0.04 (0.00 - 0.10) 0.0 0.0 0.0 0.0

mountain chickadee 0.00 0.07 (0.00 - 0.15) 100.0 0.0 0.0 100.0

horned lark 0.00 0.11 (0.00 - 0.29) 100.0 0.0 0.0 100.0

American kestrel 0.00 0.04 (0.00 - 0.10) 100.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 101 (m) and a hub height of 80 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 3.0-MW turbine rotor-swept area (RSA) 1 during Winter 2010 30-minute point count 

survey at the National Wind Technology Center.

Table 6m.

common raven 0.05 0.07 (0.00 - 0.14) 100.0 0.0 75.0 25.0

western meadowlark 0.00 0.10 (0.01 - 0.19) 0.0 0.0 0.0 0.0

red-tailed hawk 0.00 0.12 (0.03 - 0.21) 14.3 0.0 0.0 100.0

rough-legged hawk 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

mountain bluebird 0.00 0.13 (0.00 - 0.35) 0.0 0.0 0.0 0.0

downy woodpecker 0.00 0.05 (0.00 - 0.11) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.02 (0.00 - 0.05) 0.0 0.0 0.0 0.0

black-capped chickadee 0.00 0.07 (0.00 - 0.18) 0.0 0.0 0.0 0.0

black-billed magpie 0.00 0.15 (0.03 - 0.27) 55.6 0.0 0.0 100.0

American robin 0.00 0.05 (0.00 - 0.13) 0.0 0.0 0.0 0.0

American kestrel 0.00 0.05 (0.00 - 0.10) 33.3 0.0 0.0 100.0

1

These values assume a rotor diameter of 100 (m) and a hub height of 90 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 3.0-MW turbine rotor-swept area (RSA) 1 during Spring 2010 30-minute point count 

ོ

surveys at the National Wind Technology Center.

Table 6n.

turkey vulture 0.04 0.10 (0.00 - 0.20) 100.0 0.0 42.9 57.1

common raven 0.01 0.13 (0.05 - 0.21) 100.0 0.0 11.1 88.9

red-tailed hawk 0.01 0.04 (0.00 - 0.08) 66.7 0.0 50.0 50.0

ferruginous hawk 0.01 0.01 (0.00 - 0.03) 100.0 0.0 100.0 0.0

Wilson's snipe 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

western meadowlark 0.00 1.17 (0.95 - 1.39) 4.8 0.0 0.0 100.0

western kingbird 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

vesper sparrow 0.00 0.69 (0.39 - 0.99) 0.0 0.0 0.0 0.0

spotted towhee 0.00 0.08 (0.01 - 0.15) 0.0 0.0 0.0 0.0

Say's phoebe 0.00 0.03 (0.00 - 0.06) 0.0 0.0 0.0 0.0

red-winged blackbird 0.00 0.06 (0.00 - 0.12) 100.0 0.0 0.0 100.0

northern harrier 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

mourning dove 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

mallard 0.00 0.08 (0.00 - 0.16) 100.0 0.0 0.0 100.0

loggerhead shrike 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

killdeer 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

horned lark 0.00 0.01 (0.00 - 0.03) 0.0 0.0 0.0 0.0

European starling 0.00 0.15 (0.04 - 0.26) 54.5 0.0 0.0 100.0

Eurasian collared-dove 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

common grackle 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

broad-tailed hummingbird 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

Brewer's blackbird 0.00 0.18 (0.05 - 0.31) 76.9 0.0 0.0 100.0

black-billed magpie 0.00 0.13 (0.04 - 0.22) 22.2 0.0 0.0 100.0

barn swallow 0.00 0.18 (0.00 - 0.36) 69.2 0.0 0.0 100.0

American robin 0.00 0.11 (0.05 - 0.17) 37.5 0.0 0.0 100.0

American kestrel 0.00 0.08 (0.02 - 0.14) 33.3 0.0 0.0 100.0

American goldfinch 0.00 0.01 (0.00 - 0.03) 100.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 100 (m) and a hub height of 90 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 30 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 3.0-MW turbine rotor-swept area (RSA) 1 during early Summer 2010 30-minute point count 

surveys at the National Wind Technology Center.

Table 6o.

Wilson's snipe 0.00 0.18 (0.00 - 0.39) 0.0 0.0 0.0 0.0

western meadowlark 0.00 1.53 (1.00 - 2.06) 3.8 0.0 0.0 100.0

western kingbird 0.00 0.24 (0.02 - 0.46) 50.0 0.0 0.0 100.0

vesper sparrow 0.00 1.94 (1.26 - 2.62) 3.0 0.0 0.0 100.0

turkey vulture 0.00 0.18 (0.02 - 0.34) 100.0 0.0 0.0 100.0

spotted towhee 0.00 0.18 (0.00 - 0.47) 0.0 0.0 0.0 0.0

Say's phoebe 0.00 0.06 (0.00 - 0.16) 100.0 0.0 0.0 100.0

red-tailed hawk 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

horned lark 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

house finch 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

grasshopper sparrow 0.00 0.18 (0.02 - 0.34) 0.0 0.0 0.0 0.0

European starling 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

common raven 0.00 0.06 (0.00 - 0.16) 100.0 0.0 0.0 100.0

blue jay 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

brown-headed cowbird 0.00 0.06 (0.00 - 0.16) 0.0 0.0 0.0 0.0

barn swallow 0.00 0.53 (0.00 - 1.30) 0.0 0.0 0.0 0.0

American robin 0.00 0.18 (0.02 - 0.34) 0.0 0.0 0.0 0.0

American goldfinch 0.00 0.12 (0.00 - 0.31) 0.0 0.0 0.0 0.0

1

These values assume a rotor diameter of 100 (m) and a hub height of 90 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 3.0-MW turbine rotor-swept area (RSA) 1 during late Summer 2010 20-minute point count surveys

at the National Wind Technology Center.

Table 6p.

horned lark 0.08 1.21 (0.82 - 1.60) 46.8 0.0 13.6 86.4

common raven 0.05 0.15 (0.04 - 0.26) 33.3 0.0 100.0 0.0

grasshopper sparrow 0.03 1.36 (0.35 - 2.37) 54.7 0.0 3.4 96.6

western meadowlark 0.00 1.85 (1.30 - 2.40) 27.8 0.0 0.0 100.0

western kingbird 0.00 1.18 (0.55 - 1.81) 37.0 0.0 0.0 100.0

vesper sparrow 0.00 0.95 (0.11 - 1.79) 35.1 0.0 0.0 100.0

unidentified bird 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

tree swallow 0.00 0.56 (0.00 - 1.20) 100.0 0.0 0.0 100.0

Townsend’s solitaire 0.00 0.08 (0.00 - 0.21) 0.0 0.0 0.0 0.0

song sparrow 0.00 0.18 (0.02 - 0.34) 14.3 0.0 0.0 100.0

Say's phoebe 0.00 0.38 (0.14 - 0.62) 66.7 0.0 0.0 100.0

red-winged blackbird 0.00 2.54 (0.00 - 6.76) 94.9 0.0 0.0 100.0

red-tailed hawk 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

mourning dove 0.00 0.28 (0.10 - 0.46) 54.5 0.0 0.0 100.0

loggerhead shrike 0.00 0.05 (0.00 - 0.13) 50.0 0.0 0.0 100.0

house finch 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

gray catbird 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

European starling 0.00 0.05 (0.00 - 0.13) 0.0 0.0 0.0 0.0

Eurasian collared-dove 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

chipping sparrow 0.00 0.51 (0.28 - 0.74) 30.0 0.0 0.0 100.0

broad-tailed hummingbird 0.00 0.08 (0.01 - 0.15) 66.7 0.0 0.0 100.0

Brewer's blackbird 0.00 0.74 (0.00 - 1.68) 89.7 0.0 0.0 100.0

black-capped chickadee 0.00 0.08 (0.00 - 0.17) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

barn swallow 0.00 0.41 (0.12 - 0.70) 93.8 0.0 0.0 100.0

American goldfinch 0.00 0.08 (0.01 - 0.15) 66.7 0.0 0.0 100.0

1

These values assume a rotor diameter of 100 (m) and a hub height of 90 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 3.0-MW turbine rotor-swept area (RSA) 1 during Fall 2010 20-minute point count surveys at the

National Wind Technology Center.

Table 6q.

sandhill crane 0.06 0.06 (0.00 - 0.16) 100.0 0.0 100.0 0.0

song sparrow 0.05 0.38 (0.09 - 0.67) 58.3 0.0 21.4 78.6

mourning dove 0.03 0.22 (0.08 - 0.36) 85.7 0.0 16.7 83.3

red-tailed hawk 0.01 0.06 (0.00 - 0.12) 75.0 0.0 33.3 66.7

western meadowlark 0.00 0.46 (0.17 - 0.75) 20.7 0.0 0.0 100.0

western kingbird 0.00 0.03 (0.00 - 0.08) 0.0 0.0 0.0 0.0

vesper sparrow 0.00 0.06 (0.00 - 0.12) 75.0 0.0 0.0 100.0

unidentified sparrow 0.00 0.08 (0.01 - 0.15) 0.0 0.0 0.0 0.0

unidentified songbird 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

unidentified bird 0.00 0.05 (0.00 - 0.11) 33.3 0.0 0.0 100.0

sharp-shinned hawk 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

Say's phoebe 0.00 0.05 (0.00 - 0.11) 33.3 0.0 0.0 100.0

northern flicker 0.00 0.06 (0.00 - 0.12) 75.0 0.0 0.0 100.0

mountain chickadee 0.00 0.03 (0.00 - 0.07) 0.0 0.0 0.0 0.0

loggerhead shrike 0.00 0.02 (0.00 - 0.05) 100.0 0.0 0.0 100.0

horned lark 0.00 0.32 (0.13 - 0.51) 65.0 0.0 0.0 100.0

grasshopper sparrow 0.00 0.24 (0.08 - 0.40) 40.0 0.0 0.0 100.0

gray catbird 0.00 0.03 (0.00 - 0.07) 50.0 0.0 0.0 100.0

downy woodpecker 0.00 0.08 (0.00 - 0.19) 0.0 0.0 0.0 0.0

dark-eyed junco 0.00 0.03 (0.00 - 0.07) 100.0 0.0 0.0 100.0

Brewer's sparrow 0.00 0.08 (0.00 - 0.19) 60.0 0.0 0.0 100.0

Brewer's blackbird 0.00 0.16 (0.00 - 0.42) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.17 (0.06 - 0.28) 81.8 0.0 0.0 100.0

barn swallow 0.00 0.16 (0.00 - 0.32) 100.0 0.0 0.0 100.0

American tree sparrow 0.00 0.06 (0.00 - 0.12) 50.0 0.0 0.0 100.0

American robin 0.00 0.02 (0.00 - 0.05) 0.0 0.0 0.0 0.0

American kestrel 0.00 0.05 (0.01 - 0.09) 66.7 0.0 0.0 100.0

American goldfinch 0.00 0.17 (0.04 - 0.30) 72.7 0.0 0.0 100.0

American crow 0.00 0.06 (0.01 - 0.11) 50.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 100 (m) and a hub height of 90 (m)
Encounter

Rate

Percent

 Below RSA

Height

Percent

At RSA

 Height

Percent

Above RSA

Height

Species

Mean Use

# birds/ 20 min.

(90% confidence interval)

Percent

 Flying

Avian flight height characteristics in relation to the 3.0-MW turbine rotor- swept area (RSA) 1 during Winter 2010-2011 20-minute point count surveys

at the National Wind Technology Center.

Table 6r.

common raven 0.04 0.25 (0.09 - 0.41) 71.4 0.0 20.0 80.0

unidentified songbird 0.00 0.04 (0.00 - 0.10) 0.0 0.0 0.0 0.0

red-tailed hawk 0.00 0.04 (0.00 - 0.10) 100.0 0.0 0.0 100.0

northern flicker 0.00 0.04 (0.00 - 0.10) 0.0 0.0 0.0 0.0

mountain chickadee 0.00 0.07 (0.00 - 0.15) 100.0 0.0 0.0 100.0

horned lark 0.00 0.11 (0.00 - 0.29) 100.0 0.0 0.0 100.0

black-billed magpie 0.00 0.68 (0.09 - 1.27) 94.7 0.0 0.0 100.0

American kestrel 0.00 0.04 (0.00 - 0.10) 100.0 0.0 0.0 100.0

1

These values assume a rotor diameter of 100 (m) and a hub height of 90 (m)
Species

Table 7a. Incidental observations of birds during 30-minute point count surveys at the National Wind Technology Center and off-site reference 

 locations, 2010.

Number of

birds

Winter 2010 Spring 2010 Summer 2010 Overall

Number of

birds

Number of

birds

Number of

birds

American kestrel 1 0 0 1

black-billed magpie 9 0 0 9

Canada goose 20 0 0 20

common raven 15 0 0 15

European starling 8 0 0 8

mallard 10 0 0 10

mountain bluebird 25 0 0 25

rough-legged hawk 1 0 0 1

red-tailed hawk 8 0 0 8

red-winged blackbird 1 0 0 1

Grand Total 98 0 0 98
Species

Table 7b. Incidental observations of birds during 20-minute point count surveys at the National Wind Technology Center, 2010-2011.

Number of

birds

Summer 2010 Fall 2010 Winter 2010-2011 Overall

Number of

birds

Number of

birds

Number of

birds

American goldfinch 4 15 0 19

American robin 0 5 0 5

barn swallow 6 15 0 21

Brewer's blackbird 11 0 0 11

broad-tailed hummingbird 2 0 0 2

chipping sparrow 1 0 0 1

ferruginous hawk 1 0 0 1

gray catbird 1 0 0 1

grasshopper sparrow 14 0 0 14

mourning dove 19 0 0 19

northern harrier 0 1 0 1

rock pigeon 0 50 0 50

red-tailed hawk 3 0 0 3

red-winged blackbird 43 0 0 43

Say's phoebe 2 0 0 2

song sparrow 0 30 0 30

Swainson’s hawk 1 0 0 1

unidentified bird 0 30 0 30

unidentified hawk 0 7 0 7

vesper sparrow 10 5 0 15

western kingbird 9 2 0 11

western meadowlark 9 15 0 24

American kestrel 0 0 1 1

black-billed magpie 6 1 3 10

common raven 2 1 4 7

European starling 30 0 6 36

horned lark 30 35 10 75
Species

Table 7b. Incidental observations of birds during 20-minute point count surveys at the National Wind Technology Center, 2010-2011.

Number of

birds

Summer 2010 Fall 2010 Winter 2010-2011 Overall

Number of

birds

Number of

birds

Number of

birds

Canada goose 0 0 19 19

Grand Total 204 212 43 459
Species

Table 7c. Incidental observations of birds during 20-minute point count surveys at Boulder County, 2010-2011.

Number of

birds

Summer 2010 Fall 2010 Winter 2010-2011 Overall

Number of

birds

Number of

birds

Number of

birds

black-billed magpie 0 1 0 1

Brewer's blackbird 1 0 0 1

grasshopper sparrow 1 0 0 1

mourning dove 2 0 0 2

red-winged blackbird 4 0 0 4

Say's phoebe 1 0 0 1

Swainson’s hawk 1 0 0 1

unidentified hawk 0 1 0 1

vesper sparrow 1 1 0 2

western meadowlark 5 2 0 7

American kestrel 0 1 1 2

red-tailed hawk 0 0 1 1

common raven 0 0 2 2

horned lark 3 3 2 8

Canada goose 0 0 11 11

Grand Total 19 9 17 45
Species

Table 7d. Incidental observations of birds during point 20-minute count surveys at Rocky Flats, 2010-2011.

Number of

birds

Summer 2010 Fall 2010 Winter 2010-2011 Overall

Number of

birds

Number of

birds

Number of

birds

American kestrel 1 1 0 2

barn swallow 3 0 0 3

chipping sparrow 0 3 0 3

red-winged blackbird 4 0 0 4

Swainson’s hawk 4 0 0 4

tree swallow 1 0 0 1

vesper sparrow 0 7 0 7

western kingbird 1 0 0 1

black-billed magpie 0 3 1 4

golden eagle 0 1 1 2

northern harrier 0 4 1 5

prairie falcon 0 0 1 1

great horned owl 0 0 2 2

red-tailed hawk 1 0 3 4

western meadowlark 3 2 7 12

American tree sparrow 0 3 26 29

horned lark 1 6 60 67

Grand Total 19 30 102 151
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 8a. Non-raptor species observed by point during 10-minute point count surveys at the National

 Wind Technology Center, Winter 2010. 

black-billed magpie 9 5 4 0 0 0 1 4

mountain bluebird 8 1 0 0 8 0 0 0

western meadowlark 6 5 0 0 0 4 1 1

common raven 4 3 2 0 1 0 0 1

black-capped chickadee 4 1 4 0 0 0 0 0

downy woodpecker 3 2 3 0 0 0 0 0

American robin 3 2 3 0 0 0 0 0

dark-eyed junco 1 1 1 0 0 0 0 0

Grand Total 38 20 17 0 9 4 2 6
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 8b. Non-raptor species observed by point during 10-minute point count surveys at the National

 Wind Technology Center, Spring 2010.

western meadowlark 84 74 12 9 15 16 17 15

vesper sparrow 50 29 4 7 14 9 5 11

Brewer's blackbird 13 7 0 3 3 2 5 0

barn swallow 13 4 10 1 0 0 0 2

European starling 11 6 1 3 2 1 4 0

common raven 9 7 0 3 2 1 1 2

black-billed magpie 9 6 2 0 0 0 3 4

American robin 8 8 5 1 0 0 0 2

spotted towhee 6 5 3 0 0 0 0 3

mallard 6 5 0 3 0 0 1 2

red-winged blackbird 4 3 1 2 0 0 1 0

western kingbird 2 1 0 0 0 2 0 0

Say's phoebe 2 2 0 1 0 0 0 1

Eurasian collared-dove 2 1 2 0 0 0 0 0

dark-eyed junco 2 1 2 0 0 0 0 0

Wilson's snipe 1 1 0 0 0 0 0 1

mourning dove 1 1 1 0 0 0 0 0

loggerhead shrike 1 1 0 0 0 0 1 0

killdeer 1 1 1 0 0 0 0 0

horned lark 1 1 0 1 0 0 0 0

common grackle 1 1 1 0 0 0 0 0

broad-tailed hummingbird 1 1 0 0 0 0 1 0

American goldfinch 1 1 1 0 0 0 0 0

Grand Total 229 167 46 34 36 31 39 43
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 8c. Non-raptor species observed by point during 10-minute point count surveys at the National Wind

 Technology Center, Summer 2010. 

red-winged blackbird 97 9 0 93 0 0 1 3

western meadowlark 73 67 11 11 10 28 8 5

vesper sparrow 55 47 13 8 11 5 12 6

grasshopper sparrow 34 26 9 8 2 7 3 5

western kingbird 32 21 4 11 1 13 1 2

horned lark 32 25 1 4 6 8 7 6

barn swallow 22 13 6 3 11 0 1 1

chipping sparrow 14 14 3 2 4 3 0 2

Brewer's blackbird 14 4 0 13 0 0 1 0

Say's phoebe 11 10 7 4 0 0 0 0

tree swallow 7 1 0 0 0 0 7 0

mourning dove 7 7 1 1 1 2 1 1

common raven 6 5 3 0 0 1 0 2

American goldfinch 4 3 1 0 0 0 0 3

Wilson's snipe 3 2 0 0 0 0 0 3

spotted towhee 3 3 3 0 0 0 0 0

song sparrow 3 3 0 0 2 0 1 0

black-capped chickadee 3 3 0 1 0 0 2 0

American robin 3 3 2 0 0 0 0 1

house finch 2 2 0 0 0 1 1 0

European starling 2 2 0 1 1 0 0 0

loggerhead shrike 1 1 0 0 0 0 1 0

gray catbird 1 1 1 0 0 0 0 0

broad-tailed hummingbird 1 1 0 0 1 0 0 0

blue jay 1 1 1 0 0 0 0 0

brown-headed cowbird 1 1 1 0 0 0 0 0

black-billed magpie 1 1 0 0 0 0 1 0

Grand Total 433 276 67 160 50 68 48 40
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 8d. Non-raptor species observed by point during 10-minute point count surveys at the National Wind

 Technology Center, Fall 2010.

western meadowlark 18 15 1 3 1 6 1 6

horned lark 14 9 2 2 0 5 1 4

song sparrow 12 10 2 7 0 2 1 0

grasshopper sparrow 12 8 1 5 0 3 3 0

mourning dove 10 5 2 6 2 0 0 0

Brewer's blackbird 10 1 0 10 0 0 0 0

American goldfinch 6 3 1 0 0 1 0 4

vesper sparrow 4 3 2 0 1 0 1 0

sandhill crane 4 1 0 0 0 0 0 4

black-billed magpie 4 4 2 0 0 0 0 2

American tree sparrow 4 3 3 0 0 0 0 1

barn swallow 3 3 0 1 2 0 0 0

western kingbird 2 1 0 0 0 0 2 0

unidentified sparrow 2 2 1 1 0 0 0 0

Say's phoebe 2 2 2 0 0 0 0 0

mountain chickadee 2 2 2 0 0 0 0 0

downy woodpecker 2 2 2 0 0 0 0 0

American crow 2 2 0 1 1 0 0 0

dark-eyed junco 1 1 1 0 0 0 0 0

Grand Total 114 77 24 36 7 17 9 21
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 8e. Avian species observed by point during 10-minute point count surveys at the National

 Wind Technology Center, Winter 2010-2011.

common raven 3 3 0 0 1 1 0 1

black-billed magpie 3 3 1 0 0 0 0 2

northern flicker 1 1 1 0 0 0 0 0

mountain chickadee 1 1 1 0 0 0 0 0

Grand Total 8 8 3 0 1 1 0 3
Number

of

Birds

Species

Number

of

Obs.

Points

NW-01 NW-02 NW-03 NW-04 NW-05 NW-06

Table 8f. Non-ratpor species observed by point during 10-minute point count surveys at the National Wind

 Technology Center from 01/13/2010 through 02/14/2011.

western meadowlark 181 161 24 23 26 54 27 27

vesper sparrow 109 79 19 15 26 14 18 17

red-winged blackbird 101 12 1 95 0 0 2 3

horned lark 47 35 3 7 6 13 8 10

grasshopper sparrow 46 34 10 13 2 10 6 5

barn swallow 38 20 16 5 13 0 1 3

Brewer's blackbird 37 12 0 26 3 2 6 0

western kingbird 36 23 4 11 1 15 3 2

black-billed magpie 26 19 9 0 0 0 5 12

common raven 22 18 5 3 4 3 1 6

mourning dove 18 13 4 7 3 2 1 1

song sparrow 15 13 2 7 2 2 2 0

Say's phoebe 15 14 9 5 0 0 0 1

chipping sparrow 14 14 3 2 4 3 0 2

American robin 14 13 10 1 0 0 0 3

European starling 13 8 1 4 3 1 4 0

American goldfinch 11 7 3 0 0 1 0 7

spotted towhee 9 8 6 0 0 0 0 3

mountain bluebird 8 1 0 0 8 0 0 0

tree swallow 7 1 0 0 0 0 7 0

black-capped chickadee 7 4 4 1 0 0 2 0

mallard 6 5 0 3 0 0 1 2

downy woodpecker 5 4 5 0 0 0 0 0

Wilson's snipe 4 3 0 0 0 0 0 4

sandhill crane 4 1 0 0 0 0 0 4

dark-eyed junco 4 3 4 0 0 0 0 0

American tree sparrow 4 3 3 0 0 0 0 1

mountain chickadee 3 3 3 0 0 0 0 0

unidentified sparrow 2 2 1 1 0 0 0 0

loggerhead shrike 2 2 0 0 0 0 2 0

house finch 2 2 0 0 0 1 1 0

Eurasian collared-dove 2 1 2 0 0 0 0 0

broad-tailed hummingbird 2 2 0 0 1 0 1 0

American crow 2 2 0 1 1 0 0 0

northern flicker 1 1 1 0 0 0 0 0

killdeer 1 1 1 0 0 0 0 0

gray catbird 1 1 1 0 0 0 0 0

common grackle 1 1 1 0 0 0 0 0

blue jay 1 1 1 0 0 0 0 0

brown-headed cowbird 1 1 1 0 0 0 0 0

Grand Total 822 548 157 230 103 121 98 113
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 8g. Non-raptor species observed by point during 10-minute point count surveys at off-site reference locations, 

 Winter 2010.

horned lark 26 15 1 2 20 0 2 1

Canada goose 25 1 0 0 0 25 0 0

black-billed magpie 13 5 0 0 0 0 1 12

common raven 10 7 3 4 0 2 1 0

mountain bluebird 6 1 0 0 0 6 0 0

European starling 3 1 0 0 0 0 0 3

red-winged blackbird 2 1 0 0 0 2 0 0

western meadowlark 1 1 0 0 0 0 0 1

dark-eyed junco 1 1 0 0 0 1 0 0

Grand Total 87 33 4 6 20 36 4 17
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 8h. Non-raptor species observed by point during 10-minute point count surveys at off-site reference 

 locations, Spring 2010.

red-winged blackbird 132 14 35 0 0 93 0 4

western meadowlark 121 79 24 20 19 23 17 18

horned lark 69 25 3 9 19 8 11 19

vesper sparrow 65 29 7 10 5 28 9 6

Franklin’s gull 40 1 0 0 40 0 0 0

American pipit 23 3 3 20 0 0 0 0

American crow 21 4 6 15 0 0 0 0

cedar waxwing 16 2 0 0 6 0 0 10

mountain bluebird 12 2 0 12 0 0 0 0

European starling 12 4 9 0 0 0 3 0

American robin 12 7 0 0 0 5 2 5

barn swallow 11 4 0 0 0 8 3 0

black-billed magpie 7 5 0 0 0 2 2 3

common raven 6 4 0 0 0 2 3 1

mallard 5 4 4 0 0 1 0 0

long-billed curlew 5 1 0 0 5 0 0 0

common grackle 4 3 0 3 0 0 1 0

Canada goose 4 4 2 0 0 2 0 0

Wilson's snipe 3 2 0 0 0 1 2 0

western kingbird 3 3 0 0 0 2 0 1

mourning dove 3 2 0 0 0 3 0 0

killdeer 2 2 1 0 0 1 0 0

broad-tailed hummingbird 2 2 0 0 0 0 1 1

Brewer's blackbird 2 2 0 2 0 0 0 0

tree swallow 1 1 0 0 0 0 1 0

spotted towhee 1 1 0 0 0 1 0 0

red-headed woodpecker 1 1 0 0 0 0 0 1

ruby-crowned kinglet 1 1 0 0 0 1 0 0

loggerhead shrike 1 1 0 0 0 0 1 0

grasshopper sparrow 1 1 0 0 0 0 1 0

great blue heron 1 1 0 0 0 1 0 0

Bullock's oriole 1 1 0 0 0 1 0 0

Grand Total 588 216 94 91 94 183 57 69
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 8i. Non-raptor species observed by point during 10-minute point count surveys at off-site reference

 locations, Summer 2010.

horned lark 71 35 7 13 9 3 35 4

western meadowlark 57 57 10 15 18 5 3 6

grasshopper sparrow 44 28 14 7 11 8 2 2

red-winged blackbird 14 14 2 3 0 3 5 1

vesper sparrow 9 9 0 4 3 0 1 1

American goldfinch 8 2 0 0 0 0 5 3

western kingbird 7 7 5 0 1 0 1 0

Say's phoebe 6 6 3 0 1 0 1 1

barn swallow 5 3 0 2 0 0 1 2

chipping sparrow 4 4 1 0 0 1 2 0

mourning dove 3 3 0 0 0 2 0 1

common raven 3 3 1 0 1 0 1 0

song sparrow 2 2 0 0 0 2 0 0

broad-tailed hummingbird 2 2 1 0 0 0 0 1

Brewer's blackbird 2 1 0 0 2 0 0 0

spotted towhee 1 1 0 0 0 1 0 0

savannah sparrow 1 1 0 1 0 0 0 0

Grand Total 239 178 44 45 46 25 57 22
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 8j. Non-raptor species observed by point during 10-minute point count surveys at off-site reference

 locations, Fall 2010. 

western meadowlark 87 33 7 57 5 5 7 6

vesper sparrow 33 8 0 2 0 3 26 2

song sparrow 29 15 2 2 12 3 4 6

lark bunting 12 2 0 0 12 0 0 0

horned lark 12 11 0 3 3 1 5 0

black-billed magpie 12 10 3 2 0 6 0 1

grasshopper sparrow 5 5 0 0 2 0 2 1

American tree sparrow 5 4 0 0 2 1 2 0

western kingbird 4 4 0 0 1 1 2 0

red-winged blackbird 4 3 0 0 0 0 1 3

mourning dove 4 3 1 2 0 1 0 0

unidentified bird 2 2 0 0 1 0 0 1

Say's phoebe 2 2 0 0 0 2 0 0

hairy woodpecker 2 1 0 0 0 0 2 0

common raven 2 1 0 0 2 0 0 0

Brewer's sparrow 2 2 0 0 0 0 1 1

American goldfinch 2 2 0 1 0 1 0 0

unidentified sparrow 1 1 1 0 0 0 0 0

northern flicker 1 1 0 0 1 0 0 0

gray catbird 1 1 0 0 0 1 0 0

European starling 1 1 0 0 1 0 0 0

chipping sparrow 1 1 0 1 0 0 0 0

black-capped chickadee 1 1 0 0 0 1 0 0

American crow 1 1 0 1 0 0 0 0

Grand Total 226 115 14 71 42 26 52 21
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 8k. Non-raptor species observed by point during 10-minute point count surveys at off-site reference

 locations Winter 2010-2011.

unidentified songbird 8 2 0 0 0 0 0 8

common raven 4 3 1 1 2 0 0 0

western meadowlark 2 1 0 0 0 0 0 2

black-billed magpie 1 1 0 0 0 1 0 0

Grand Total 15 7 1 1 2 1 0 10
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 8l. Non-raptor species observed by point during 10-minute point count surveys at off-site reference locations 

 from 01/13/2010 through 02/14/2011.

western meadowlark 268 171 41 92 42 33 27 33

horned lark 178 86 11 27 51 12 53 24

red-winged blackbird 152 32 37 3 0 98 6 8

vesper sparrow 107 46 7 16 8 31 36 9

grasshopper sparrow 50 34 14 7 13 8 5 3

Franklin’s gull 40 1 0 0 40 0 0 0

black-billed magpie 33 21 3 2 0 9 3 16

song sparrow 31 17 2 2 12 5 4 6

Canada goose 29 5 2 0 0 27 0 0

common raven 25 18 5 5 5 4 5 1

American pipit 23 3 3 20 0 0 0 0

American crow 22 5 6 16 0 0 0 0

mountain bluebird 18 3 0 12 0 6 0 0

European starling 16 6 9 0 1 0 3 3

cedar waxwing 16 2 0 0 6 0 0 10

barn swallow 16 7 0 2 0 8 4 2

western kingbird 14 14 5 0 2 3 3 1

lark bunting 12 2 0 0 12 0 0 0

American robin 12 7 0 0 0 5 2 5

mourning dove 10 8 1 2 0 6 0 1

American goldfinch 10 4 0 1 0 1 5 3

unidentified songbird 8 2 0 0 0 0 0 8

Say's phoebe 8 8 3 0 1 2 1 1

mallard 5 4 4 0 0 1 0 0

long-billed curlew 5 1 0 0 5 0 0 0

chipping sparrow 5 5 1 1 0 1 2 0

American tree sparrow 5 4 0 0 2 1 2 0

common grackle 4 3 0 3 0 0 1 0

broad-tailed hummingbird 4 4 1 0 0 0 1 2

Brewer's blackbird 4 3 0 2 2 0 0 0

Wilson's snipe 3 2 0 0 0 1 2 0

unidentified bird 2 2 0 0 1 0 0 1

spotted towhee 2 2 0 0 0 2 0 0

killdeer 2 2 1 0 0 1 0 0

hairy woodpecker 2 1 0 0 0 0 2 0

Brewer's sparrow 2 2 0 0 0 0 1 1

unidentified sparrow 1 1 1 0 0 0 0 0

tree swallow 1 1 0 0 0 0 1 0

savannah sparrow 1 1 0 1 0 0 0 0

red-headed woodpecker 1 1 0 0 0 0 0 1

ruby-crowned kinglet 1 1 0 0 0 1 0 0

northern flicker 1 1 0 0 1 0 0 0

loggerhead shrike 1 1 0 0 0 0 1 0
Number

of

Birds

Species

Number

of

Obs.

Points

CB-01 CB-02 CB-03 RF-01 RF-02 RF-03

Table 8l. Non-raptor species observed by point during 10-minute point count surveys at Off-site reference locations 

 from 01/13/2010 through 02/14/2011.

gray catbird 1 1 0 0 0 1 0 0

great blue heron 1 1 0 0 0 1 0 0

dark-eyed junco 1 1 0 0 0 1 0 0

Bullock's oriole 1 1 0 0 0 1 0 0

black-capped chickadee 1 1 0 0 0 1 0 0

Grand Total 1155 549 157 214 204 271 170 139
Carcass Size Season Number

Searcher

Efficiency Lower CI Upper CI

Bat Winter 16 0.38 0.19 0.56

Bat Spring 8 0.63 0.36 0.88

Large Winter 11 0.73 0.46 0.91

Large Spring 9 0.55 0.22 0.79

Large Summer 11 0.73 0.5 0.91

Small Winter 8 0.37 0.13 0.63

Small Spring 19 0.63 0.45 0.79

Small Summer 25 0.20 0.08 0.32

Pooled Pooled 107 0.49 0.40 0.56

Carcass Size Season Number

Carcass

Persistence Lower CI Upper CI

Bat Winter 3 32.37 26.25 38.75

Bat Winter 1 30.00 30.00 30.00

Large Winter 10 70.50 67.13 72.75

Large Spring 10 2.88 2.50 3.40

Large Summer 10 134.77 117.00 150.00

Small Winter 13 36.38 30.63 41.88

Small Spring 15 2.50 2.50 2.50

Small Summer 15 26.11 19.90 32.70

Pooled Pooled 77 24.8 19.08 32.86

Table 9. Bootstrapped searcher efficiency (probability that a carcass is found) and

 carcass persistence (days) estimates and 90 percent confidence intervals (CI).
Fall and Winter ‐ 10 of 11 sites searched.

Estimate Lower Upper Estimate Lower CI Upper CI

Bats 6 16 13 49 1.45 1.15 4.43

Birds1 1 3 2 8 0.22 0.19 0.66

1Only one small bird was found.

Spring and Summer ‐ 11 of 11 sites searched.

Estimate Lower Upper Estimate Lower CI Upper CI

Bats 7 17 3 45 1.53 0.19 4.04

Birds1 4 10 5 17 0.85 0.38 1.47

1 All were small birds.

Table 10. Bootstrapped fatality estimates and 90 percent confidence intervals derived using the 

 Huso Estimator.

Category # found

Total Site Fatality Estimate Fatality Estimate per Turbine

Category # found

Total Site Fatality Estimate Fatality Estimate per Turbine
Avian Monitoring and Mortality Report 

National Wind Technology Center 

 October 2011 

APPENDICES 
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1a. Flight directions of birds observed during Winter 2010 30-minute point count surveys at the National Wind Technology Center.

Percentage of Flights

N NE E SE S SW W NW Variable

black-billed magpie 5 3 0.0 0.0 20.0 0.0 0.0 0.0 20.0 0.0 0.0

common raven 2 2 0.0 0.0 0.0 50.0 50.0 0.0 0.0 0.0 0.0

rough-legged hawk 1 1 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Grand Total 8 6 12.5 0.0 12.5 12.5 12.5 0.0 12.5 0.0 0.0

1

 Includes only flying birds with flight directions
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1b. Flight directions of birds observed during Spring 2010 30-minute point count surveys at the National Wind Technology Center.

Percentage of Flights

N NE E SE S SW W NW Variable

barn swallow 7 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

turkey vulture 4 2 25.0 0.0 0.0 0.0 0.0 0.0 0.0 75.0 0.0

European starling 3 1 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0

Brewer's blackbird 3 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

red-tailed hawk 2 2 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

common raven 1 1 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0

common grackle 1 1 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0

black-billed magpie 1 1 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

American robin 1 1 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0

Grand Total 23 11 8.7 0.0 8.7 4.3 13.0 0.0 52.2 13.0 0.0

1

 Includes only flying birds with flight directions
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1c. Flight directions of birds observed during late Summer 2010 20-minute point count surveys at the National Wind Technology Center.

Percentage of Flights

N NE E SE S SW W NW Variable

Brewer's blackbird 25 5 56.0 0.0 0.0 0.0 4.0 0.0 0.0 40.0 0.0

barn swallow 14 12 7.1 7.1 21.4 0.0 7.1 21.4 21.4 14.3 0.0

horned lark 11 7 9.1 9.1 9.1 27.3 9.1 0.0 36.4 0.0 0.0

western meadowlark 10 7 0.0 0.0 60.0 10.0 0.0 10.0 10.0 10.0 0.0

grasshopper sparrow 9 7 0.0 11.1 11.1 11.1 33.3 0.0 33.3 0.0 0.0

tree swallow 6 4 16.7 0.0 16.7 0.0 33.3 33.3 0.0 0.0 0.0

Say's phoebe 6 5 50.0 0.0 0.0 0.0 16.7 0.0 33.3 0.0 0.0

vesper sparrow 5 4 80.0 0.0 20.0 0.0 0.0 0.0 0.0 0.0 0.0

chipping sparrow 5 5 40.0 0.0 0.0 0.0 0.0 0.0 40.0 20.0 0.0

red-winged blackbird 4 4 50.0 0.0 0.0 0.0 25.0 0.0 25.0 0.0 0.0

mourning dove 4 4 0.0 0.0 0.0 0.0 0.0 50.0 25.0 25.0 0.0

common raven 2 1 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0

black-capped chickadee 2 2 0.0 0.0 50.0 50.0 0.0 0.0 0.0 0.0 0.0

American goldfinch 2 2 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0

western kingbird 1 1 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0

unidentified bird 1 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

song sparrow 1 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

Eurasian collared-dove 1 1 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

broad-tailed hummingbird 1 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

Grand Total 110 74 26.4 2.7 16.4 5.5 10.0 7.3 18.2 13.6 0.0

1

 Includes only flying birds with flight directions
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1d. Flight directions of birds observed during Fall 2010 20-minute point count surveys at the National Wind Technology Center.

Percentage of Flights

N NE E SE S SW W NW Variable

song sparrow 14 7 7.1 0.0 7.1 0.0 0.0 0.0 57.1 28.6 0.0

mourning dove 12 6 41.7 0.0 16.7 0.0 0.0 0.0 33.3 0.0 8.3

Brewer's blackbird 10 1 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

barn swallow 10 7 20.0 20.0 50.0 10.0 0.0 0.0 0.0 0.0 0.0

horned lark 7 4 42.9 0.0 0.0 0.0 42.9 0.0 14.3 0.0 0.0

black-billed magpie 7 4 0.0 0.0 14.3 42.9 28.6 0.0 14.3 0.0 0.0

American goldfinch 7 4 0.0 0.0 14.3 0.0 0.0 0.0 85.7 0.0 0.0

grasshopper sparrow 6 3 0.0 0.0 16.7 0.0 50.0 0.0 33.3 0.0 0.0

western meadowlark 5 2 0.0 0.0 20.0 80.0 0.0 0.0 0.0 0.0 0.0

sandhill crane 4 1 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0

vesper sparrow 3 2 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

northern flicker 3 3 0.0 0.0 0.0 0.0 66.7 33.3 0.0 0.0 0.0

Brewer's sparrow 3 1 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0

red-tailed hawk 2 1 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0

dark-eyed junco 2 2 0.0 0.0 0.0 0.0 50.0 0.0 0.0 50.0 0.0

American tree sparrow 2 1 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0

American kestrel 2 2 0.0 0.0 0.0 0.0 50.0 0.0 50.0 0.0 0.0

American crow 2 2 0.0 0.0 50.0 50.0 0.0 0.0 0.0 0.0 0.0

unidentified bird 1 1 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0

sharp-shinned hawk 1 1 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0

loggerhead shrike 1 1 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0

Grand Total 104 56 23.1 1.9 15.4 10.6 17.3 3.8 22.1 4.8 1.0

1

 Includes only flying birds with flight directions
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1e. Flight directions of birds observed during Winter 2010-2011 20-minute point count surveys at the National Wind Technology Center.

Percentage of Flights

N NE E SE S SW W NW Variable

common raven 5 5 60.0 0.0 0.0 0.0 20.0 0.0 20.0 0.0 0.0

black-billed magpie 5 4 20.0 0.0 80.0 0.0 0.0 0.0 0.0 0.0 0.0

red-tailed hawk 1 1 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0

mountain chickadee 1 1 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0

Grand Total 12 11 33.3 0.0 33.3 0.0 16.7 8.3 8.3 0.0 0.0

1

 Includes only flying birds with flight directions
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1f. Flight directions of birds observed during Winter 2010 30-minute point count surveys at the off-site reference locations.

Percentage of Flights

N NE E SE S SW W NW Variable

Canada goose 25 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

horned lark 13 3 0.0 0.0 0.0 76.9 0.0 0.0 0.0 0.0 0.0

black-billed magpie 6 2 66.7 0.0 0.0 33.3 0.0 0.0 0.0 0.0 0.0

European starling 3 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0

common raven 2 2 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0

red-tailed hawk 1 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

golden eagle 1 1 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0

Grand Total 51 11 7.8 0.0 0.0 29.4 0.0 0.0 51.0 5.9 0.0

1

 Includes only flying birds with flight directions
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1g. Flight directions of birds observed during Spring 2010 30-minute point count surveys at the off-site reference locations.

Percentage of Flights

N NE E SE S SW W NW Variable

red-winged blackbird 15 2 0.0 6.7 0.0 0.0 93.3 0.0 0.0 0.0 0.0

barn swallow 5 2 0.0 40.0 0.0 0.0 0.0 0.0 0.0 60.0 0.0

common raven 2 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0

American robin 2 1 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

western meadowlark 1 1 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0

tree swallow 1 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

red-tailed hawk 1 1 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

red-headed woodpecker 1 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

mourning dove 1 1 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 0.0

broad-tailed hummingbird 1 1 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0

bald eagle 1 1 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

American crow 1 1 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 0.0

Grand Total 32 14 3.1 18.8 3.1 3.1 43.8 3.1 6.3 15.6 0.0

1

 Includes only flying birds with flight directions
Number

 of

Birds1

Number

of

Observations

Species

Appendix 1h. Flight directions of birds observed during early Summer 2010 30-minute point count surveys at the off-site reference locations.

Percentage of Flights

N NE E SE S SW W NW Variable

vesper sparrow 1 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Grand Total 1 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

1

 Includes only flying birds with flight directions
Appendix 2a. Avian percent composition and frequency, sorted by species group, observed during 30-minute point count surveys at the

 National Wind Technology Center, 2010.

Species

Species Group

Winter 2010 Spring 2010 Summer 2010

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

Songbirds

western meadowlark 12.2 6.7 34.0 63.9 26.3 82.4 29.4 43.0

vesper sparrow 0.0 0.0 20.2 34.7 33.3 88.2 21.0 26.8

barn swallow 0.0 0.0 5.3 5.6 9.1 11.8 5.6 4.0

black-billed magpie 18.4 8.3 3.6 8.3 0.0 0.0 4.6 7.4

common raven 8.2 5.0 3.6 9.7 1.0 5.9 3.5 7.4

American robin 6.1 1.7 3.2 11.1 3.0 17.6 3.5 8.1

Brewer's blackbird 0.0 0.0 5.3 8.3 0.0 0.0 3.3 4.0

European starling 0.0 0.0 4.5 8.3 1.0 5.9 3.0 4.7

spotted towhee 0.0 0.0 2.4 5.6 3.0 5.9 2.3 3.4

mountain bluebird 16.3 1.7 0.0 0.0 0.0 0.0 2.0 0.7

western kingbird 0.0 0.0 0.8 1.4 4.0 17.6 1.5 2.7

red-winged blackbird 0.0 0.0 1.6 4.2 0.0 0.0 1.0 2.0

black-capped chickadee 8.2 1.7 0.0 0.0 0.0 0.0 1.0 0.7

Say's phoebe 0.0 0.0 0.8 2.8 1.0 5.9 0.8 2.0

horned lark 0.0 0.0 0.4 1.4 2.0 5.9 0.8 1.3

grasshopper sparrow 0.0 0.0 0.0 0.0 3.0 17.6 0.8 2.0

dark-eyed junco 2.0 1.7 0.8 1.4 0.0 0.0 0.8 1.3

American goldfinch 0.0 0.0 0.4 1.4 2.0 5.9 0.8 1.3

loggerhead shrike 0.0 0.0 0.4 1.4 0.0 0.0 0.3 0.7

house finch 0.0 0.0 0.0 0.0 1.0 5.9 0.3 0.7

common grackle 0.0 0.0 0.4 1.4 0.0 0.0 0.3 0.7

blue jay 0.0 0.0 0.0 0.0 1.0 5.9 0.3 0.7

brown-headed cowbird 0.0 0.0 0.0 0.0 1.0 5.9 0.3 0.7

Group Total 71.4 87.9 91.9 86.8

Raptors

red-tailed hawk 14.3 8.3 1.2 4.2 2.0 5.9 3.0 6.0

turkey vulture 0.0 0.0 2.8 4.2 3.0 17.6 2.5 4.0
Appendix 2a. Avian percent composition and frequency, sorted by species group, observed during 30-minute point count surveys at the

 National Wind Technology Center, 2010.

Species

Species Group

Winter 2010 Spring 2010 Summer 2010

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

American kestrel 6.1 5.0 2.4 6.9 0.0 0.0 2.3 5.4

rough-legged hawk 2.0 1.7 0.0 0.0 0.0 0.0 0.3 0.7

northern harrier 0.0 0.0 0.4 1.4 0.0 0.0 0.3 0.7

ferruginous hawk 0.0 0.0 0.4 1.4 0.0 0.0 0.3 0.7

Group Total 22.4 7.3 5.1 8.6

Waterfowl

mallard 0.0 0.0 2.4 4.2 0.0 0.0 1.5 2.0

Group Total 0.0 2.4 0.0 1.5

Waterbirds

Wilson's snipe 0.0 0.0 0.4 1.4 3.0 11.8 1.0 2.0

killdeer 0.0 0.0 0.4 1.4 0.0 0.0 0.3 0.7

Group Total 0.0 0.8 3.0 1.3

Woodpeckers

downy woodpecker 6.1 3.3 0.0 0.0 0.0 0.0 0.8 1.3

Group Total 6.1 0.0 0.0 0.8

Pigeons/Doves

Eurasian collared-dove 0.0 0.0 0.8 1.4 0.0 0.0 0.5 0.7

mourning dove 0.0 0.0 0.4 1.4 0.0 0.0 0.3 0.7

Group Total 0.0 1.2 0.0 0.8

Swifts/Hummingbirds

broad-tailed hummingbird 0.0 0.0 0.4 1.4 0.0 0.0 0.3 0.7

Group Total 0.0 0.4 0.0 0.3

Grand Total 100.0% 100.0% 100.0% 100.0%

* Percent composition is the fraction of the total number of individuals
Appendix 2b. Avian percent composition and frequency, sorted by species group, observed during 20-minute point count surveys at the National Wind Technology 

 Center, 2010-2011.

Species

Species Group

Summer 2010 Fall 2010 Winter 2010-2011

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

Songbirds

western meadowlark 14.3 69.2 14.1 20.6 0.0 0.0 13.6 30.8

red-winged blackbird 19.7 17.9 0.0 0.0 0.0 0.0 13.3 5.4

horned lark 9.4 59.0 9.8 14.3 8.6 3.6 9.4 25.4

grasshopper sparrow 10.6 51.3 7.3 11.1 0.0 0.0 9.2 20.8

western kingbird 9.2 38.5 1.0 1.6 0.0 0.0 6.5 12.3

vesper sparrow 7.4 17.9 2.0 4.8 0.0 0.0 5.5 7.7

Brewer's blackbird 5.8 12.8 4.9 1.6 0.0 0.0 5.3 4.6

song sparrow 1.4 10.3 11.7 12.7 0.0 0.0 4.2 9.2

black-billed magpie 0.2 2.6 5.4 12.7 54.3 21.4 4.2 11.5

barn swallow 3.2 30.8 4.9 4.8 0.0 0.0 3.5 11.5

tree swallow 4.4 15.4 0.0 0.0 0.0 0.0 3.0 4.6

chipping sparrow 4.0 30.8 0.0 0.0 0.0 0.0 2.7 9.2

Say's phoebe 3.0 23.1 1.5 3.2 0.0 0.0 2.4 8.5

American goldfinch 0.6 7.7 5.4 11.1 0.0 0.0 1.9 7.7

common raven 1.2 12.8 0.0 0.0 20.0 21.4 1.8 8.5

unidentified sparrow 0.0 0.0 2.4 6.3 0.0 0.0 0.7 3.1

Brewer's sparrow 0.0 0.0 2.4 3.2 0.0 0.0 0.7 1.5

mountain chickadee 0.0 0.0 1.0 3.2 5.7 7.1 0.5 3.1

American tree sparrow 0.0 0.0 2.0 4.8 0.0 0.0 0.5 2.3

American crow 0.0 0.0 2.0 6.3 0.0 0.0 0.5 3.1

unidentified songbird 0.0 0.0 1.0 3.2 2.9 3.6 0.4 2.3

Townsend’s solitaire 0.6 2.6 0.0 0.0 0.0 0.0 0.4 0.8

loggerhead shrike 0.4 2.6 0.5 1.6 0.0 0.0 0.4 1.5

gray catbird 0.2 2.6 1.0 3.2 0.0 0.0 0.4 2.3

black-capped chickadee 0.6 5.1 0.0 0.0 0.0 0.0 0.4 1.5

European starling 0.4 2.6 0.0 0.0 0.0 0.0 0.3 0.8

dark-eyed junco 0.0 0.0 1.0 3.2 0.0 0.0 0.3 1.5
Appendix 2b. Avian percent composition and frequency, sorted by species group, observed during 20-minute point count surveys at the National Wind Technology 

 Center, 2010-2011.

Species

Species Group

Summer 2010 Fall 2010 Winter 2010-2011

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

house finch 0.2 2.6 0.0 0.0 0.0 0.0 0.1 0.8

American robin 0.0 0.0 0.5 1.6 0.0 0.0 0.1 0.8

Group Total 96.6 81.5 91.4 92.2

Pigeons/Doves

mourning dove 2.2 28.2 6.8 11.1 0.0 0.0 3.4 13.8

Eurasian collared-dove 0.2 2.6 0.0 0.0 0.0 0.0 0.1 0.8

Group Total 2.4 6.8 0.0 3.5

Raptors

red-tailed hawk 0.2 2.6 2.0 4.8 2.9 3.6 0.8 3.8

American kestrel 0.0 0.0 1.5 4.8 2.9 3.6 0.5 3.1

sharp-shinned hawk 0.0 0.0 0.5 1.6 0.0 0.0 0.1 0.8

Group Total 0.2 3.9 5.7 1.5

Woodpeckers

northern flicker 0.0 0.0 2.0 4.8 2.9 3.6 0.7 3.1

downy woodpecker 0.0 0.0 2.4 3.2 0.0 0.0 0.7 1.5

Group Total 0.0 4.4 2.9 1.3

Other

unidentified bird 0.2 2.6 1.5 3.2 0.0 0.0 0.5 2.3

Group Total 0.2 1.5 0.0 0.5

Cranes/Rails

sandhill crane 0.0 0.0 2.0 1.6 0.0 0.0 0.5 0.8

Group Total 0.0 2.0 0.0 0.5

Swifts/Hummingbirds

broad-tailed hummingbird 0.6 7.7 0.0 0.0 0.0 0.0 0.4 2.3

Group Total 0.6 0.0 0.0 0.4

Grand Total 100.0% 100.0% 100.0% 100.0%
Appendix 2c. Avian percent composition and frequency, sorted by species group, observed during 30-minute point count surveys at the off-site reference locations, 2010.

Species

Species Group

Winter 2010 Spring 2010 Summer 2010

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

Songbirds

red-winged blackbird 2.1 1.9 21.9 11.1 0.0 0.0 18.7 6.5

western meadowlark 1.1 1.9 20.1 77.8 47.4 58.3 18.3 46.4

horned lark 27.4 20.4 11.4 26.4 0.0 0.0 13.2 21.7

vesper sparrow 0.0 0.0 10.8 37.5 21.1 33.3 9.6 22.5

American pipit 0.0 0.0 3.8 2.8 0.0 0.0 3.2 1.4

American crow 0.0 0.0 3.5 5.6 0.0 0.0 2.9 2.9

black-billed magpie 13.7 9.3 1.2 6.9 0.0 0.0 2.8 7.2

mountain bluebird 6.3 1.9 2.0 1.4 0.0 0.0 2.5 1.4

common raven 10.5 11.1 1.0 5.6 5.3 8.3 2.4 8.0

cedar waxwing 0.0 0.0 2.7 2.8 0.0 0.0 2.2 1.4

European starling 3.2 1.9 2.0 5.6 0.0 0.0 2.1 3.6

American robin 0.0 0.0 2.0 9.7 0.0 0.0 1.7 5.1

barn swallow 0.0 0.0 1.8 5.6 0.0 0.0 1.5 2.9

common grackle 0.0 0.0 0.7 2.8 0.0 0.0 0.6 1.4

western kingbird 0.0 0.0 0.5 4.2 0.0 0.0 0.4 2.2

spotted towhee 0.0 0.0 0.2 1.4 5.3 8.3 0.3 1.4

Brewer's blackbird 0.0 0.0 0.3 1.4 0.0 0.0 0.3 0.7

tree swallow 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

ruby-crowned kinglet 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

loggerhead shrike 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

grasshopper sparrow 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

dark-eyed junco 1.1 1.9 0.0 0.0 0.0 0.0 0.1 0.7
Appendix 2c. Avian percent composition and frequency, sorted by species group, observed during 30-minute point count surveys at the off-site reference locations, 2010.

Species

Species Group

Winter 2010 Spring 2010 Summer 2010

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

Bullock's oriole 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

Group Total 65.3 86.6 78.9 83.5

Gulls/Terns

Franklin’s gull 0.0 0.0 6.6 1.4 0.0 0.0 5.6 0.7

Group Total 0.0 6.6 0.0 5.6

Waterfowl

Canada goose 26.3 1.9 0.7 2.8 0.0 0.0 4.0 2.2

mallard 0.0 0.0 0.8 4.2 0.0 0.0 0.7 2.2

Group Total 26.3 1.5 0.0 4.7

Raptors

red-tailed hawk 4.2 5.6 0.5 2.8 5.3 8.3 1.1 4.3

American kestrel 0.0 0.0 0.8 6.9 10.5 8.3 1.0 4.3

Swainson’s hawk 0.0 0.0 0.5 4.2 0.0 0.0 0.4 2.2

great horned owl 2.1 3.7 0.2 1.4 0.0 0.0 0.4 2.2

turkey vulture 0.0 0.0 0.3 1.4 0.0 0.0 0.3 0.7

northern harrier 1.1 1.9 0.0 0.0 0.0 0.0 0.1 0.7

golden eagle 1.1 1.9 0.0 0.0 0.0 0.0 0.1 0.7

bald eagle 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

Group Total 8.4 2.5 15.8 3.6

Waterbirds

long-billed curlew 0.0 0.0 0.8 1.4 0.0 0.0 0.7 0.7

Wilson's snipe 0.0 0.0 0.5 2.8 0.0 0.0 0.4 1.4
Appendix 2c. Avian percent composition and frequency, sorted by species group, observed during 30-minute point count surveys at the off-site reference locations, 2010.

Species

Species Group

Winter 2010 Spring 2010 Summer 2010

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

killdeer 0.0 0.0 0.3 2.8 0.0 0.0 0.3 1.4

great blue heron 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

Group Total 0.0 1.8 0.0 1.5

Pigeons/Doves

mourning dove 0.0 0.0 0.5 2.8 5.3 8.3 0.6 2.2

Group Total 0.0 0.5 5.3 0.6

Swifts/Hummingbirds

broad-tailed hummingbird 0.0 0.0 0.3 2.8 0.0 0.0 0.3 1.4

Group Total 0.0 0.3 0.0 0.3

Woodpeckers

red-headed woodpecker 0.0 0.0 0.2 1.4 0.0 0.0 0.1 0.7

Group Total 0.0 0.2 0.0 0.1

Grand Total 100.0% 100.0% 100.0% 100.0%

* Percent composition is the fraction of the total number of individuals
Appendix 2d. Avian percent composition and frequency, sorted by species group, observed during 30-minute point count surveys at the off-site reference

 locations, 2010-2011.

Species

Species Group

Summer 2010 Fall 2010 Winter 2010-2011

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

Songbirds

western meadowlark 17.0 58.5 33.4 36.2 6.1 3.0 23.7 35.0

horned lark 22.1 53.7 4.2 11.6 12.1 9.1 13.8 23.1

grasshopper sparrow 16.5 53.7 3.6 8.7 0.0 0.0 10.2 19.6

European starling 15.0 2.4 1.2 1.4 0.0 0.0 8.3 1.4

song sparrow 0.8 4.9 11.6 13.0 0.0 0.0 5.5 7.7

vesper sparrow 1.3 4.9 10.1 8.7 0.0 0.0 5.1 5.6

red-winged blackbird 5.0 41.5 2.7 8.7 0.0 0.0 3.8 16.1

black-billed magpie 0.0 0.0 6.0 17.4 3.0 3.0 2.7 9.1

western kingbird 2.8 22.0 2.7 7.2 0.0 0.0 2.6 9.8

American tree sparrow 0.0 0.0 3.3 7.2 18.2 6.1 2.2 4.9

lark bunting 0.3 2.4 3.6 1.4 0.0 0.0 1.7 1.4

American goldfinch 2.8 7.3 0.6 2.9 0.0 0.0 1.7 3.5

unidentified songbird 0.3 2.4 0.0 0.0 27.3 6.1 1.3 2.1

Say's phoebe 1.8 17.1 0.9 4.3 0.0 0.0 1.3 7.0

barn swallow 2.5 14.6 0.0 0.0 0.0 0.0 1.3 4.2

tree swallow 2.3 7.3 0.0 0.0 0.0 0.0 1.2 2.1

common raven 0.5 4.9 0.6 1.4 15.2 12.1 1.2 4.9

chipping sparrow 1.5 12.2 0.9 2.9 0.0 0.0 1.2 4.9

Brewer's blackbird 2.3 7.3 0.0 0.0 0.0 0.0 1.2 2.1

unidentified sparrow 0.0 0.0 2.1 10.1 0.0 0.0 0.9 4.9

American crow 0.0 0.0 2.1 7.2 0.0 0.0 0.9 3.5

Brewer's sparrow 0.0 0.0 1.5 4.3 0.0 0.0 0.7 2.1

lark sparrow 0.5 2.4 0.0 0.0 0.0 0.0 0.3 0.7

savannah sparrow 0.3 2.4 0.0 0.0 0.0 0.0 0.1 0.7

gray catbird 0.0 0.0 0.3 1.4 0.0 0.0 0.1 0.7

black-capped chickadee 0.0 0.0 0.3 1.4 0.0 0.0 0.1 0.7

Group Total 95.2 91.6 81.8 93.1
Appendix 2d. Avian percent composition and frequency, sorted by species group, observed during 20-minute point count surveys at the off-site reference 

 locations, 2010-2011.

Species

Species Group

Summer 2010 Fall 2010 Winter 2010-2011

Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency Percent

Comp.

Frequency

Overall

% of surveys

detected

% of surveys

detected

% of surveys

detected

% of surveys

detected

Raptors

American kestrel 2.0 14.6 2.4 5.8 0.0 0.0 2.1 7.0

turkey vulture 0.0 0.0 1.5 4.3 0.0 0.0 0.7 2.1

red-tailed hawk 0.0 0.0 0.6 2.9 9.1 6.1 0.7 2.8

northern harrier 0.0 0.0 0.0 0.0 9.1 9.1 0.4 2.1

Group Total 2.0 4.5 18.2 3.8

Pigeons/Doves

mourning dove 1.8 9.8 2.4 7.2 0.0 0.0 2.0 6.3

Group Total 1.8 2.4 0.0 2.0

Woodpeckers

hairy woodpecker 0.0 0.0 0.6 1.4 0.0 0.0 0.3 0.7

northern flicker 0.0 0.0 0.3 1.4 0.0 0.0 0.1 0.7

Group Total 0.0 0.9 0.0 0.4

Swifts/Hummingbirds

broad-tailed hummingbird 0.8 7.3 0.0 0.0 0.0 0.0 0.4 2.1

Group Total 0.8 0.0 0.0 0.4

Other

unidentified bird 0.0 0.0 0.6 2.9 0.0 0.0 0.3 1.4

Group Total 0.0 0.6 0.0 0.3

Waterfowl

greater scaup 0.3 2.4 0.0 0.0 0.0 0.0 0.1 0.7

Group Total 0.3 0.0 0.0 0.1

Grand Total 100.0% 100.0% 100.0% 100.0%

* Percent composition is the fraction of the total number of individuals
Fatality Photos 

Available photographs of fatalities included here show position of fatality as found and 

distance to closest vertical structure. 
Fall Survey Week 1 – 9.9.2010 

Site 4.4 – SILVER-HAIRED BAT (No Photos Available) 

Site 4.4 – SILVER-HAIRED BAT (No Photos Available) 

Site 4.4 – HOARY BAT (No Photos Available) 

Site 4.4 – UNKNOWN BAT (No Photos Available) 

 
Fall Survey Week 2 – 9.13.2010 

Site M-2 – MOURNING DOVE (FEATHER SPOT) 
Site 4.4 – HOARY BAT 

 
Site 4.4 – UNKNOWN BAT 

Spring Survey Week 9 –5.18.2011 

Site 4.4 – UNKNOWN SPARROW (No Photos Available) 

 
Summer Survey Week 1 – 6.9.2011 

Site 4.3 – UNKNOWN PASSERINE 

 
Summer Survey Week 3 – 6.15.2011 

Site 4.1 – SILVER-HAIRED BAT 

 
Summer Survey Week 8 – 7.28.2011 

Site 3.4 – BLACK-BILLED MAGPIE 

 
Summer Survey Week 11 – 8.18.2011 

Site 4.1 – HOARY BAT 
Site 4.1 – BIG BROWN BAT 

 
Summer Survey Week 12 – 8.22.2011 

Site 4.1 – BIG BROWN BAT 

 
Summer Survey Week 13 – 9.2.2011 

Site 4.1 – HOARY BAT 

Site 4.1 – BIG BROWN BAT (No Photos Available) 

 
Site 4.1 – HOARY BAT