HomeMy WebLinkAboutApplication section 9Report on Bat Activity in Enfield, NY
Report on Bat Activity
in Enfield, NY
Prepared for:
Enfield Energy
Prepared by:
Integrated Environmental Data, LLC
1330 Bradt Hollow Rd.
Berne, NY 12023
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in,forinaiion for wise decisions
December, 2009
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Report on Bat Activity in Enfield, NY
Executive Summary
This study consisted of passive monitoring of bat activity in one location and during
one season in the town of Enfield. Activity was monitored near the crossroads of Black Oak
Road and Cayutaville Road from August 24, 2009 until October 9, 2009. The monitor was
provided by IED and installed on the met tower by Prevailing Winds and John Rancich of
Enfield Energy.
At least three bat species were documented at the site. The presence of a fourth species
is highly likely, based on a small number of calls. The bats were most active at wind speeds
varying from 3 to 7 meters per second (m/s). The most common species appear to be
Eptisicus fuscus and Myotis lucifugus. For the entire monitoring period, bats were present on
39 of 69 monitoring nights. Bats were present on 28 of the first 32 nights of monitoring
(August 24 to Sept 25).
Site Description
The Enfield met tower is in an exposed hay field at an elevation of approximately
580 meters. A buried pipeline transmission power line right of way is located in the same
field less than 100 meters away at the closest point. A scrap and metal recycling center is
somewhat over 100 in to the north west of the tower. Radio towers occupy the hilltop
directly to the south, across Cayutaville Road.. A portion of Robert H. Treman State Park
shares a contiguous border with the area, also on the South side of Cayutaville road. To the
west, the area shares a contiguous border with the Connecticut Hill State Wildlife
Management Area. Both the state park and the wildlife management area are well forested
with a mix of mature hemlocks, mixed hardwoods and some white pine.
The Enfield land cover and land use map classifies the immediate area around the
tower as "agricultural". The NYS DEC has classified the stream that drains the property to
the west, which enters a ravine and becomes a tributary of Cayuga Inlet. DEC and the NY
Natural Heritage Program do not list any rare plants, rare animals, state registered wetlands or
significant natural communities as residing in the immediate area or in the adjoining forests,
according to the present data base. '
According to the USGS Bat Population Database bat species historically in
residence in Tomkins county include: Myotis leibii, the rare, eastern small -footed bat, Myotis
lucifugus the little brown bat, and Perimyotis subflavans (formerly Pipistrellus subflavans)
the eastern pipistrelle. Myotis leibii is listed as a species of concern by the NY Natural
Heritage Program. The endangered Myotis sodalis (Indiana Bat) has not been recorded in
Tompkins County. The site is not within 40 miles of a known M. soda/ishibemaculum, the
radius defined in the NYSDEC guidelines for wind energy projects.
Methods
An Anabat SDI was used for this study. The SDI detector was installed in a
waterproof housing at the base of a,6,0 m met tower. It was continuously powered during the
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study period by a solar panel which charged a 12 V battery. A Hi Mic microphone was
installed at 50 meters while the tower was down for maintenance and connected to the SD 1
by cable. The CF cards for the SDI were programmed to collect data from 18:00 to 07:00
hours, EDT. The Anabat settings, in accordance with established protocols, were as follows:
audio division 16, data division 8, sensitivity settings of 6 to 7.
The CF card was checked within 4$ hours of installation and was operating optimally,
based on the number and quality of recordings on the first two nights. CF cards were
switched every two weeks through the bat activity period.
Raw data files from the SD 1 are large and therefore were archived to an external disk.
The cfcread program provided by Titley Scientific was used to produce Anabat files, which
were in turn analyzed using the AnalookW software package, also from Titley Scientific.
Both programs were produced by C. Corben. Software documentation was obtained from M.
J. O'Farrell.
Based on recorded calls, bats were sorted into species groups. The five groups for
which the recordings were examined are shown in Table 1. Calls distorted by, environmental
noise or other factors were classified as unknown species. The identification of individual
species within some groups isnot.reliable with passive monitoring alone. Each recording
event may contain multiple calls and is therefore referred to as a call sequence. In general,
recordings that contained only one call were classified as unidentified,bat species:
Table 1
Group
number and
ID
1 EELnoct
12 MY
13 Pip
4 Lac
5 Lab
Species in group
Historically
present
EptisicusfuscuslLasionycteris noctivagans_
N
Myotis species-
Y
Perimyotis subf avans
Y
Lasiurus cinereus
IN
Lasiurus borealis
I N
Data from AnabatW recordings was matched with met tower data using R functions,
producing a continuous data set for the period. The data set was analyzed using both R and
excel functions.
Results
The monitoring period was sustained for 69 nights. Bat calls were recorded on 39
nights in a total of 166 call sequences. Fifty-three percent (53 %) of the calls could be placed
in a species group while 47%'of the calls could not be sorted into species due to
environmental noise or distortion. Only three of the five species groups were observed.
(Table 2). In addition to bat calls, environmental noise, especially high winds, triggered
almost 70 thousand recording events. Eighty-seven percent (87%) of these noise events
occurred between October 1I and October 31. Identifiable bat call sequences represent 1.7%
of the recordings made between August 24 and October 10, but only 0.2% of recordings after
October 10. Bat activity decreased sharply during high wind events in October.
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On nights when bats were present, an average of 4.3 bat call sequences were recorded.
For the entire measuring period, including nights without bat recordings, there were an
average of 2.4 call sequences per night recorded. On twenty-one nights (30 % of the
recording time), 2 or more species were present during the night -long recording period.
Table 2
Species group
Epitisicus fucusl
Lasionycterius noctivagans
Myotis spp. _-
j Lasiurus cinerus
Bat calls not identified to species
Discussion
Number of Number of nights
recordings recorded
53 24
24 9
11 7
78 28 1
Seasonal Activity — Bat activity declined sharply after September twenty-fifth. Before
September 26th, bat calls were absent on only four nights of monitoring. From the 26th
onward, bats were detected only nine of thirty-six nights; bats calls were absent in monitoring
on 75% of nights in late September and October. This coincides with a period of lower
temperatures and generally rising wind speeds. All late season calls (after October tenth)
were in the Big Brown group or were unidentifiable.
Figure 1- Bat call sequences from August 24 (day 236) to October 24 (day 297)
R
f
235 238 240 ?_42 244 246 248 250 253 255. 2.58 251 253 265 258 275 230 283 293 297
Figure 1 summarizes the day of year and number of call sequences recorded over the entire
monitoring period.
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Species of Interest —NYSDEC guidelines 3 have identified three species of special interest
in wind turbine construction monitoring: the red (Lasiurus borealis), hoary (Lasiurus
cinereus) , and silver -haired bats (Lasionycteris noctivagans). In this study, the hoary bat was
positively identified by call on 11 occasions. Although the silver bat was grouped with the
big brown bat because of the overlap in their call frequencies, on two occasions it was
possible to detect durations and inflections that are signatures of the silver bat and indicate its
presence in the area.
The Myotis species complex also exhibits overlapping call frequency ranges, but the
inflection and duration of the vast majority of calls indicates that M. lucifugus is the dominant
Myotis species in the area. No Myotis calls in this study carried the signature of M_ sodalis,
the endangered Indiana bat. Some calls which were un -interpretable due to environmental
distortion might have been of M. sodalis, but this is unlikely given the site location and
history. Similarly, the presence or absence of M. leibii, a species of concern, cannot be
inferred from this sampling method alone.
Although historically common in Tompkins county, no pipistrelle bats (Perimyotis
subflavus) were observed during the monitoring period.
Weather and Bats — In general, bats were active at higher wind speeds in Enfield than might
be expected from recent impact mitigation literature z. Figure 2 illustrates overall bat activity
at increasing wind speeds. In order to illustrate the expected results of mitigation (e.g.
curtailing turbine activity at wind speeds below 4 M/s), the horizontal axis of wind speeds
shows the lowest value in. the next data bin, in other words, "1 m/s" on -the graph represents
wind speeds of 0 to 0.99 m/s while "10 m/s" represents 9 to 9.99 m/s
Figure 2 — Changes in all bat activity at increasing wind speeds
Number of Bat Call Sequences by Wind Speed
9 9 10 12
Figure 2 illustrates that bat. activity peaks at speeds of 3 to 4 meters per second,
however, the greatest total amount of activity occurs between :3 and 7 m/s.
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Figure 3 — Effect of wind speed on bat activity
Big Brom Bat and Myotis Species by Wind Speed
�� Hid 3szrxn
t:4Yotis �I
7 4 G7 8
'Hind speed, rr:'s
Activity of different species complexes is not uniform with changes in wind speed. Although
Myotis spp. and the Big Brown bat group were both active at wind speeds between 3 and 7
m/s, the Myotis group appears to have a more narrow tolerance for wind variation (Figure 3).
The Big Brown species group also persisted in the area later into the season when high wind
events were more common. It cannot be determined from this study if this is the result of
wind and weather tolerance alone or if the absence of prey species influenced the Myotis bats.
Myotis bats might have been more commonly recorded if a second microphone had been used
at a 2-3 meter height on the tower.
Figure 4 Effect of wind speed on bat activity
Hoary and Unidentified Bat Species by wind Speed
iim Hoary
A Unld
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Figure 4 shows activity of the Hoary Bat and the unidentified bats in the study.
Numbers of clear Hoary Bat call sequences were small. Like the Big Brown group, the Hoary
bat is active at a wider range of wind speeds than the Myotis group-. Many of the bat call
sequences distorted by the wind also occur at higher wind speeds. It is likely, based on wind
speed occurrence, that the larger species, the Big Brown Bat group and the Hoary Bat, are
disproportionately represented among the unidentified group. The location of the microphone
at hub height would also skew the collection of calls toward the larger species, especially
toward the Hoary Bat. Unfortunately, the Hoary bat exhibits high variability of call
characteristics in frequency, duration and inflection 4 , making it difficult to identify this
species with certainty unless a longer sequence of calls is captured. Wind speeds above 9 m/s
make it unlikely such a sequence can be obtained..
Recent guidelines from the DEC describing bat monitoring protocols 3 underscore the
importance and the problems associated with assessing vulnerability of migratory bats such as
the Hoary bat. Lack of information about these species has caused a delay in protocol
recommendations for tracking these bats, beyond listing them as of particular interest. This is
expected to change as more data on bat mortality becomes available.
Figure 5 is a general summary of bat activity over the measurement period and
superimposes that activity on graphs of the wind speed in meters per second (middle line in
black) and temperature in degrees Celsius (top line in blue). The red bars at the bottom of the
graph are times bat call sequences were recorded. Dates given are day of the year where day
240 is August 28 and day 300 is October 27.
Figure 5 - Summary of.bat activity (red bars), wind speed and temperature
0
Oil
a: t N 1{ !
to
243 253 263 270 283 290 1300
E
m
Day of Year
Rainfall occurred on twenty-one of the thirty-nine nights when bat calls were recorded.
Although bats did not call during heavy precipitation events, they did call before and after
such events and also on nights of light rainfall.
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Conclusions
1. Bat were present at the Enfield site on 57% of sampling nights and had an average of
43 call sequences per night. This bat activity level is similar to activity at other
potential wind turbine generation sites in New York and New England. Bats are
relatively common in August and September. Overall activity decreased sharply in
October.
2. Bat species present include at least one species of concern, the hoary bat, Lasiurus
cinereus. These call sequences account for 13% of identified calls.
3. Bat activity is common at wind speeds of 3 to 7 meters per second.
References
1. http://www.fort.usgsgov/BPD/
2. Edward B. Arnett and Michael Schirmacher, Bat Conservation International, Manuela
M. P. Huso, Oregon State University, John P. Hayes, University of Florida, April
2009, Effectiveness of Changing Wind Turbine Cut -in Speed to Reduce Bat Fatalities
at Wind Facilities, 45 pp.
3. New York State Department of Environmental Conservation Division of Fish,
Wildlife and Marine Resources, January 2009, GUIDELINES -for CONDUCTING
BIRD and BAT STUDIES at COMMERCIAL WIND ENERGY PROJECTS
4. O'Farrell, M.J., B.W. Miller; -and W.L. Gannon. 2000, Geographic variation in the
echolocation calls of the hoary bat (Lasiurus cinereus). Acta Chiroptera, 2(2):185-196
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