Avian and Bat Interactions
With Turbines
Overview of Methods
and Results
March 2008
Dale Strickland
Western EcoSystems Technology, Inc.
Cheyenne, Wyoming
History of the Avian/Wind Turbine Issue
• 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)
Result: New wind plants often heavily scrutinized
1.5 MW
turbine
100 kW
turbine
Not exactly to scale
Fatality Monitoring Studies
Hopkins Ridge, WA
Combine Hills, OR
NPPD Ainsworth, NE
Condon, OR
High Winds, CA
Altamont, CA NWTC, CO
Diablo Winds, CA
Montezuma Hills, CA
Tehachapi Pass, CA
San Gorgonio, CA
Searsburg, VT
Top of Iowa
Algona Iowa
New Project since NWCC 2001 Summary
Data reported in NWCC 2001 Summary
Additional data collected since NWCC 2001 Summary
WEST, Inc.
Meyersdale, PA
Somerset, PA
1%
1% 2%
6%
1%
ALL REGIONS
1%
11%
3%
Doves/Pigeons
Gamebirds
Other Birds
Passerines
Rails/Coots
Raptors/Vultures
Shorebirds
Unidentified Birds
Waterbirds
Waterfowl
74%
Sites: BM, Mo, BR, T of I, Condon, WI, NC, SL, Van, FCR, NWTC, and Ponnequin
WEST, Inc.
All Birds
14.0
11.7
# Bird Fatalities / MW
12.0
10.0
8.0
5.9
6.0
4.0
2.0
3.3
3.0
3.1
2.8 2.9 2.6
2.7
2.0
2.5
2.0
1.8
1.4
1.0
1.0
2.5
1.4
1.3
0.0
WI B1 B2 B3
Agriculture
WEST, Inc.
TI VA NC SL CH K1 K2 HR BM MO DW HW F1
Ag / Grass / CRP
Wind Project
Forest
F2
AI
Grass / Steppe
Raptors
0.6
0.56
# Raptor Fatalities / MW
0.5
0.42
0.4
0.3
0.2
0.14
0.11
0.09
0.1
0.05
0.04
0
0.05 0.06
0
0
0.01
B2
B3
TI
0.07
0.02
0
0
0
0
0
WI
B1
Agriculture
WEST, Inc.
VA NC SL CH K1
K2 HR BM MO DW HW F1
Ag / Grass / CRP
Wind Project
Forest
F2
AI
Grass / Steppe
ds
as
in
tP
W
Co
,C
A
s,
tte
C
re
A
lM
W
in
tn
dy
.,
ID
Fl
De
at
s
se
,
W
r
A
Co tCl
ai
lu
m
m
,W
bi
a
A
Ha
Hi
tc
lls
he
,W
tt
Ho
A
R
id
pk
ge
in
,C
's
R
A
id
W
g
hi
e,
te
W
Cr
A
ee
R e k, W
ar
A
Co
do
m
n,
bi
W
ne
A
Hi
Ho
lls
,O
m
es
R
te
ad
Ro
,
os
CA
Le
ev
an
el
in
t,
g
Fo
W
Ju
ot
A
ni
e
pe
Cr
r,
ee
O
R
Bu k R
i
m
ffa
,W
lo
R
Y
id
ge
,
Kl
M
on
N
Zi
di
nt
k
el
e,
C
O
R
S t a ny
at
on
el
,
in
W
e,
A
W
A/
O
M
R
ai
de
n,
W
Co
A
nd
Te
on
ch
,O
ap
iP
R
a
W
ss
ild
,C
Ho
Bi
A
gl
ow rs e
,
W
Ca
A
ny
Ni
ne
on
,O
C
an
R
yo
n,
Dr
W
A
Sa y L
ak
n
e,
G
or
AZ
go
ni
o,
CA
on
gh
ta
m
Al
Hi
Mean us e
R aptors
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Wind-E nerg y F ac ility
• Most sites in the west have measures of
raptor use
• 12 of these sites have some measure of
fatality
Raptor Use
Raptor Fatality
Facilities
High Winds
Diablo Winds
Hopkins Ridge
Klondike
Range: 0 – 0.14/MW/yr
Klondike II
Stateline
Nine Canyon
Foote Creek Rim
Vansycle
Buffalo Ridge
Combine Hills
WEST, Inc.
FOOTE CREEK RIM WYOMING
Predictions of high raptor mortality, including golden eagles
Other confounding factors
Eagles
Use w/i rsa
Use w/i rsa
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
off rim
rim edge
on rim
0.0
Falcons
Use w/i rsa
off rim
A
Use w/i rsa
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
Over-flight
Fatality Risk
Strike Zone
Rotor Zone
Fly-thru
A Simple Stick Collision Model
Bird passage time through the
rotor:
tp=L/V= Length speed ratio (sec)
w deg/sec
Blocked Sector of Turbine Rotor:
B =tp w (deg)
Stick Bird
L
120 Degrees
Probability of collision:
Pc =Blocked Area/Disk Area
Pc =3B/(360deg)
Velocity = v P =3(L/V){w(deg/sec)/360deg}
c
To account for avoidance:
Pc =3 A (L/V){w(deg/sec)/360deg}
Stick Turbine
<1 for avoidance
where A = 1 for no behavior
>1 for attraction
Modeled Fatality Estimates
Collision 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.
Comparison of Spring Target Rates and
Migrant Fatality Rates
 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
Stateline
Parameter
OR/WA
Buffalo Ridge Nine Canyon
MN
WA
Spring Nighttime Surveillence Radar Data
sampling dates
Targets/hr/2.8 km (March 15 - May 15)
Estimated % of targets below 100 m
Width of WRA (km)
Estimated Spring Night Target Passage Rate
Spring Nighttime Migrant Fatality Data
Estimated Spring Nighttime Fatalities
Fatality Rate / Target Passage Rate
3/15-5/15/01 3/26 – 5/12/96 3/15-5/15/01
140
260
273
13.0%
not collected
14.4%
16
27
2.4
576,000
1,805,143
168,480
34
104
6
<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 them
Bats found at all wind projects studied
Bat Species Involved
photos: J.S. Altenbach
*Source: Johnson, G.D. 2005. A review of bat
mortality at Wind-energy developments in the United
States. Bat Research News 46:45-49.
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
Impacts
Habitat 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 510% of site (BLM 2005)
WEST, Inc.
Displacement Studies
• 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)
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.
Avoidance Behavior is Significant
Radar Tracks of Migrating Birds through Nysted Offshore
Windfarm for Operation in 2003
Response distance:
day = c. 3000m
night = c. 1000m
WEST, Inc.
Summary - Birds
•
•
•
•
•
WEST, Inc.
(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
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 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?