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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
WEST, Inc.
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
WEST, Inc.
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
WEST, Inc.
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)
WEST, Inc.
• 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
WEST, Inc.
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
WEST, Inc.
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
WEST, Inc.
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
WEST, Inc.
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?