March 2008

Dale StricklandWestern EcoSystems Technology,

Inc.Cheyenne, Wyoming

Avian and Bat InteractionsWith TurbinesOverview of Methods and Results

History of the Avian/Wind Turbine Issue

Result: New wind plants often heavily scrutinized

• Altamont Pass, CA– 7000+ turbines (now ~5400)

• various designs (lattice towers, guyed towers, vertical axis turbines, downwind turbines, above ground power lines)

– high number of raptor fatalities discovered – (Orloff and Flannery 1992, Smallwood and

Thelander 2004)• golden eagles (30-70 fatalities per year)• red-tailed hawks (300-500 fatalities per

year)• American kestrels (several hundred)• Burrowing owls (50-100 per year)

100 kW turbine

1.5 MW turbine

Not exactly to scale

Fatality Monitoring Studies

New Project since NWCC 2001 Summary

Data reported in NWCC 2001 Summary

Additional data collected since NWCC 2001 Summary

Condon, OR Top of Iowa

Altamont, CA

Tehachapi Pass, CASan Gorgonio, CA

Montezuma Hills, CA

Algona IowaMeyersdale, PASomerset, PANWTC, CO

Searsburg, VTCombine Hills, OR

Hopkins Ridge, WA

NPPD Ainsworth, NE

High Winds, CA

Diablo Winds, CA

WEST, Inc.

ALL REGIONS

11%

3%

74%

1%1%

2%1%6%

1%

Doves/Pigeons

Gamebirds

Other Birds

Passerines

Rails/Coots

Raptors/Vultures

Shorebirds

Unidentified Birds

Waterbirds

Waterfowl

Sites: BM, Mo, BR, T of I, Condon, WI, NC, SL, Van, FCR, NWTC, and Ponnequin

WEST, Inc.

2.0

3.3 3.0

5.9

1.41.0

2.8 2.92.6

1.0

3.1

1.3

11.7

2.7

1.81.4

2.52.0

2.5

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

WI B1 B2 B3 TI VA NC SL CH K1 K2 HR BM MO DW HW F1 F2 AI

# B

ird

Fa

talit

ies

/ M

WAll Birds

Wind Project

Agriculture Ag / Grass / CRP Forest Grass / Steppe

WEST, Inc.

0

0.04

0 0 0.01 0

0.05

0.09

0 0

0.11

0.14

00.02

0.56

0.42

0.05 0.06 0.07

0

0.1

0.2

0.3

0.4

0.5

0.6

WI B1 B2 B3 TI VA NC SL CH K1 K2 HR BM MO DW HW F1 F2 AI

# R

ap

tor

Fa

talit

ies

/ M

WRaptors

Wind Project

Agriculture Ag / Grass / CRP Forest Grass / Steppe

WEST, Inc.

• Most sites in the west have measures of raptor use

• 12 of these sites have some measure of fatality

R aptors

0.00.51.01.52.02.53.03.54.0

Hig h Winds , C

A

A ltamont P

ass, C

A

C otterel M

tn., ID

Windy F

lats , WA

Desert

C laim, W

A

C olumbia Hills

, WA

Ha tchett Ridge, C

A

Hopkin's R

idge, WA

White

Cre

ek, WA

Reardon, WA

C ombine Hills

, OR

Homestead, C

A

Rooseve

lt, W

A

Leaning J uniper, OR

F oote Cre

ek Rim

, WY

Buffalo Ridge, M

N

K londike, OR

Z intel Canyon, W

A

S ta teline , W

A/OR

Maiden, WA

C ondon, OR

Techapi Pass

, CA

Wild

Horse

, WA

B iglow Canyo

n, OR

Nine Canyon, W

A

Dry Lake, A

Z

S an Gorg

onio, CA

Wind-E nerg y F ac ility

Mea

n u

se

Raptor Use Raptor Fatality

Facilities

High Winds

Diablo Winds

Hopkins Ridge

Klondike

Klondike II

Stateline

Nine Canyon

Foote Creek Rim

Vansycle

Buffalo Ridge

Combine Hills

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Range: 0 – 0.14/MW/yr

FOOTE CREEK RIM WYOMING

Predictions of high raptor mortality, including golden eagles

Other confounding factors

Modeling

• “All models are wrong, some are useful, and we should seek those out”

• Modeling is an art, not a science

Visualization of Avian Interaction Zones Windfarm Flight Zone

Rotor Zone

Strike Zone

Over-flight

Fly-thru

Fatality Risk

120 Degrees L

Velocity = v

Stick Bird

w deg/sec

A Simple Stick Collision Model

Stick Turbine

Bird passage time through the rotor:

tp=L/V= Length speed ratio (sec)

Blocked Sector of Turbine Rotor:

B =tp w (deg)

Probability of collision:

Pc =Blocked Area/Disk Area

Pc =3B/(360deg)

Pc =3(L/V){w(deg/sec)/360deg}

To account for avoidance:

Pc =3 A (L/V){w(deg/sec)/360deg}

<1 for avoidancewhere A = 1 for no behavior >1 for attraction

Modeled Fatality EstimatesCollision Factors

P1: Pr. of Flying at or Below Maximum Tip Height - Radar Study

P2: Pr. of Encountering Swept Area, if flying at Swept Area Height - Area Calc./Simulation

P3: Pr. of Collision if Encountering Swept Area - Tucker Model

P4: Pr. of Turbine Operating During Migration - Wind Turbine Operators

P5: Non-Avoidance Probability - Who knows

P6: Pr. a bird passing over WRA collides with a turbine - Multiply Factors Above

B: # birds passing over site - Radar Study

P6*B: Estimated # of kills

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Three wind projects have conducted both fatality monitoring and radar studies for nocturnal migrants:

Buffalo Ridge, MN

Nine Canyon, WA

Stateline, WA/OR

Comparison of Spring Target Rates and Migrant Fatality Rates

Comparison of Spring Target Rates and Migrant Fatality Rates

Stateline Buffalo Ridge Nine Canyon

Parameter OR/WA MN WA

Spring Nighttime Surveillence Radar Data

sampling dates 3/15-5/15/01 3/26 – 5/12/96 3/15-5/15/01

Targets/hr/2.8 km (March 15 - May 15) 140 260 273

Estimated % of targets below 100 m 13.0% not collected 14.4%

Width of WRA (km) 16 27 2.4

Estimated Spring Night Target Passage Rate 576,000 1,805,143 168,480

Spring Nighttime Migrant Fatality Data Estimated Spring Nighttime Fatalities 34 104 6

Fatality Rate / Target Passage Rate <0.01% <0.01% <0.01%

Major Assumptions: (1) 1 target = 1 migrating bird, (2) no detection bias, (3) targets counted are migrating birds

Nocturnal Migrant Risk

• In U.S. studies, consistently most of the nocturnal migrants from radar studies observed over 500 ft

• No large mortality events documented at wind projects

• Still belief or concern over migrant mortality in bad weather or near stopover sites

If they are studied, you will find themIf they are studied, you will find themBats found at all wind projects studiedBats found at all wind projects studied

Bat Species Involved

*Source: Johnson, G.D. 2005. A review of bat mortality at Wind-energy developments in the United States. Bat Research News 46:45-49.

photos: J.S. Altenbach

Bat Fatalities

• 21 studies at 19 facilities• 5 regions in US and Canada• 0.9 – 53.3 bats/MW• Highest fatalities in the east with exception of

recent event in Alberta• 11 of the 45 species occurring in US• Heavily skewed to migratory foliage roosting

species (hoary, eastern red, silver-haired bats)• Little data from SW where Brazilian free-tailed

bat most abundant

Infrared Image of a Bat Flying Through a Wind Turbine Rotor

Multi-Stakeholder Wildlife Research • National Wind Coordinating Committee• Bat & Wind Energy Cooperative (BWEC)• Grassland Shrub Steppe Species Collaborative

Photo by Jason Horn, Boston University

Why are they colliding?• Hypotheses (Arnett et al; Kunz et al)

– Following linear corridors– Echolocation fails to detect turbines– Attracted to altered landscapes– Attracted to insects around turbines– Attracted to turbine sounds– Attracted to turbines as roosts– Attracted to magnetic fields– Bats experience decompression near blades– Thermal inversions bring them into blade range

• Other ideas (Cryan, unpublished)– Behaviorally programmed to gravitate toward and loiter around the

tallest “trees” along their migration route as a simple way of rendezvousing, and perhaps mating, with others of their kind

Habitat ImpactsHabitat Impacts

WEST, Inc.

Sources of Habitat Impact

• Direct loss of habitat– Turbine pads, roads, substations, transmission lines

• Indirect loss of habitat from behavioral response to wind plant facilities– Turbines, transmission lines, roads, human activity

• Long-term impacts– Permanent structures and/or avoidance with no

habituation

• Short-term impacts– Construction, restoration and/or habituation

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Predicted Impacts Due to Habitat Disturbance

• Temporary (construction) impacts from roads, pads, substation, etc. (estimated)– 0.4 to 3 acres/turbine

• Permanent (operations) impacts (estimated)– 0.7 to 1 acres/turbine

• Impacts and Reclamation success due to – Turbine type– Site characteristics– Reclamation plan– Climate

• Permanent footprint 5-10% of site (BLM 2005)

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• Field studies impacts of wind turbines absent for most species but impacts are likely (EXO et al. 2003)

• Grassland Songbird Displacement Studies– Buffalo Ridge, MN (Leddy 1999, Johnson et al.

2000): Small scale displacement (~80-100m)– South Dakota: 1 of 3 species (grasshopper sparrow)

showed reduced density within 150m in South Dakota (Schaffer and Johnson 2007)

– Stateline: Grasshopper sparrow showed displacement effect within 50m

– Oklahoma: No displacement for grassland species as a group (O’Connell and Piorkowski 2006)

• Ongoing and potential studies of bird displacement (e.g., Stateline, N & S Dakota, and prairie chicken in Kansas)

Displacement Studies

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Other Bird Species

• Mountain Plover – Foote Creek Rim, WY declined at wind plant, a reference area, and regionally

• Canada geese – Top of Iowa no displacement in corn fields

• Europe– Some species unaffected while certain waterfowl,

shorebirds, and songbirds avoid turbines (e.g., European golden plover, northern lapwing, Eurasian curlews)

– Pink-footed goose displaced up to 600m

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Radar Tracks of Migrating Birds through Nysted Offshore Windfarm for Operation in 2003

Response distance:

day = c. 3000mnight = c. 1000m

Avoidance Behavior is Significant

WEST, Inc.

Summary - Birds (based on existing studies at the current level of

development)

• With the possible exception of Altamont, avian risk from individual wind projects is a risk to individual birds and not populations

• Preliminary information suggests avian abundance is important factor in risk, although species behavior, technology and landscape are contributing factors

• Wind turbine lights not currently documented as a significant attractant for birds

• Effectiveness of deterrent measures uncertain • Major concern over offshore impacts is

displacement, although fatalities have not been adequately evaluated

WEST, Inc.

Summary - Bats• Fewer studies of pre-construction bat or migrant use and post-

construction fatality– Predictability very uncertain because of a lack of good

method for estimating exposure• Limited fatality studies suggest fatalities are primarily

migratory tree-roosting bats• Highest fatalities in the east with exception of recent event in

Alberta• Relatively high fatalities of Brazilian free-tailed bat in

Oklahoma suggest this species may be at similar risk to tree-roosting bats

• Cause and cure uncertain• Some mitigation measures show promise but must be evaluated

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Summary - Habitat• Estimated direct habitat impacts are relatively small for

birds• Displacement of grassland nesting birds is likely but the

magnitude is uncertain and may range from near 0 to several hundred meters for song birds and even greater for other species (e.g., nesting effects may be much larger for prairie grouse)

• Wind project (macro) and wind turbine (micro) siting believed to be best way to minimize impacts

• Mitigation measures poorly evaluated• Cumulative impacts poorly understood• Data better for wind than other sources of impact

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Priority Research NeedsPriority Research Needs

• Better synthesis of existing information• Fatalities and habitat-related impacts in unstudied and

new locations and unstudied species are needed• Estimation of exposure for nocturnal migrating

passerines and bats• Habitat fragmentation and cumulative impacts• Models for prediction of impacts and risk• Determine mitigation effectiveness• Cumulative impacts - linkage of fatality and non

fatality impacts to population dynamics and biological significance

WEST, Inc.

Questions?