Annual Report for the Maple Ridge Wind Power Project Post-construction Bird and Bat Fatality Study - 2006


Title: Annual Report for the Maple Ridge Wind Power Project Post-construction Bird and Bat Fatality Study - 2006
Publication Date:
June 25, 2007
Pages: 76

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Jain, A.; Kerlinger, P.; Curry, R.; Slobodnik, L. (2007). Annual Report for the Maple Ridge Wind Power Project Post-construction Bird and Bat Fatality Study - 2006. Report by Curry & Kerlinger LLC. pp 76.

The Maple Ridge Wind Power Project consists of 195 wind turbines and three permanent meteorology towers on the Tug Hill Plateau of Lewis County, just west of Lowville, New York. In 2005, a total of 120 Vestas wind turbines were constructed within the Phase I project area; the remaining 75 turbines in Phase IA and II of the project were constructed in May to December 2006. Each 1.65 MW turbine consists of an 80-meter-(262-foot)- tall tubular steel tower; a maximum 82-meter-(269-foot)-diameter rotor; and a nacelle which houses the generator, transformer, and power train. The towers have a base diameter of approximately 4.5m (15 feet) and a top diameter of 2.5 m (8 feet). The tower is topped by the nacelle, which is approximately 2.8m (9 feet) high and 7.6m (25 feet) long, and connects with the rotor hub. The rotor consists of three 41-m(134-foot)-long composite blades. Approximately 30% (38 out of 120) of the nacelles are equipped with L-864 FAA aviation obstruction beacons (lights) consisting of flashing strobes (red at night) and with no beacon illumination during the day. With a rotor blade oriented in the 12 o’clock position, each turbine has a maximum height of approximately 400 feet (122 meters). All components of the turbine are painted white.


During this first year pilot-project, carcass surveys were conducted at 50 out of 120 (41.7%) operational turbine sites, as well as the two meteorological towers. We completed 2,244 turbine searches over all 50 sites. Ten turbine sites were searched on a daily basis from June 17, 2006 to November 15, 2006 (127 complete rounds for a total of 1270 turbine tower searches). Ten turbine sites were searched every 3-days between June 29, 2006 and November 15, 2006 (45 complete rounds for a total of 450 turbine searches). Finally, 30 turbine sites were searched weekly (7-day sites) between July 11, 2006 and November 13, 2006, for a total of 524 total surveys (16 rounds). One meteorological tower was searched daily (97 total searches, from July 17, 2006 to November 15, 2006). The second meteorological tower was searched every 3 days (34 total searches, from July 17, 2006 to November 14, 2006).


A total of 125 avian incidents were recorded by searchers during standardized surveys, representing 30 species. Of the 30 species, there was one raptor fatality (American Kestrel), one woodpecker (Yellow-bellied Sapsucker) and three game bird fatalities (Wild Turkey). There were 104 identified incidents, involving 26 songbirds species, found during this partial year study (June 17, 2006 to November 15, 2006). Night migrants accounted for 80.0% of incidents during standardized surveys. The greatest number of bird incidents occurred during the fall migration period with 81 (64.8%; N = 125) bird carcasses found between September and October 2006. Although no waterbirds or shorebirds were found during standardized surveys, incidental findings revealed one Ruffed Grouse (game bird), and two Canada Goose carcasses (water bird). The term “incident” is used here to refer to either a fatality or injury of a bird or bat found within the wind project area and does not necessarily indicate that the cause of death or injury was wind turbine related. This term is not to be confused with the term defined earlier, “incidental find”, which refers to incidents found other than during standardized surveys and at sites outside the 50 searched towers.

Remains of 326 bats were found by searchers during standardized surveys, representing five species (Hoary Bat, Silver-haired Bat, Eastern Red Bat, Little Brown Bat, and Big Brown Bat). The greatest number of bat incidents occurred during the fall migration period, with 228 (69.9%) bat carcasses found between July 1, 2006 and August 31, 2006.


Bat carcasses appeared to fall closer to turbine tower bases than bird carcasses. Bat fatalities appeared to be slightly greater at turbines close to wetland areas than at turbines located farther from wetlands, although there was variation in these data. There did not appear to be a difference in bat or bird fatalities between wooded and non-wooded turbine sites.


Carcass removal (scavenging) and searcher efficiency studies were conducted to estimate the proportion of carcasses missed by the searchers and the proportion removed by scavengers within the one, three and 7-day search cycles. These rates, along with the proportion of towers searched were used to estimate the total number of fatalities likely to have occurred during the study period at all 120 Phase I turbines at the Maple Ridge Wind Resource Area (WRA). Carcass removal rates were modest. While carcass removal and searcher efficiency rates calculated for bats were comparable to those found in most fatality studies conducted in the United States, more effort is required for such tests in the future.


As the TAC completed authorization to proceed with searches and contract finalization in mid-May, this pilot year of the project started later than originally planned. Project setup was completed by end-August 2006, due to reasons described in the Methods. As a result, final results included below necessarily include biases including: 1-day, 3-day and 7-day sites set up in that order of priority, i.e. differing search study durations, and initial site search was affected by presence of vegetation to a greater extent at 7-day and 3-day sites. While the area searched under each tower was more than adequate to discover a majority of bat carcasses, it is likely that a number of birds fell outside the search area. Changes to the study design for subsequent years will correct for these biases, but they should be kept in mind when considering the results of the pilot year (2006).


By dividing the estimated number of incidents by the number of turbines and by 1.65 MW per turbine searched in each period, a rate of incidents/turbine and incidents/Megawatt was calculated for the study duration. Because we used three different search periods to calculate incidents/MW, we calculated three different fatality estimates for birds and bats. A typical 1.65 MW wind turbine tower in New York State will produce approx 4,400 MWh per year (William Moore, PPM-Atlantic Renewable, pers. comm.). The metric “incidents/MWh produced” is calculated for the different durations of the project period for 1, 3 and 7-Day sites. See Results for 95% CI.


The estimates for birds are:

1-Day (Total season 152 days): 1151 incidents/season, 5.81 incidents/Mw/season, 9.59 incidents/turbine/season and 0.0053 incidents/MWh/season (Megawatt-hour) produced.

3-Day (Total season 138 days): 536 incidents/season, 2.71 incidents/Mw, 4.47 incidents/turbine, and 0.0027 incidents/MWh produced.

7-Day (Total season 125 days): 376 incidents/season, 1.90 incidents/Mw, 3.13 incidents/turbine and 0.0020 incidents/MWh produced.


The estimates for bats are:

1-Day (Total season 152 days): 2943 incidents/season, 14.87 incidents/Mw, 24.53 incidents/turbine and 0.0134 incidents/MWh produced.

3-Day (Total season 138 days): 2680 incidents/season, 13.54 incidents/Mw, 22.34 incidents/turbine and 0.0133 incidents/MWh produced.

7-Day (Total season 125 days): 1824 incidents/season, 9.21 incidents/Mw, 15.20 incidents/turbine and 0.0099 incidents/MWh produced.


For both bats and birds, there is no clear evidence that L-864 FAA obstruction lighting (flashing red strobes) attracted birds or bats to towers and that the presence of those lights cause large scale fatality events at wind turbines. There was no significant difference between the numbers of birds or bats killed at turbines with vs. without L-864 obstruction lights.


As this is the pilot year of the project, comparison between initial study results and other study sites is difficult. While rates of bird and bat fatalities were within the ranges of those found during other wind turbine fatality studies conducted in the United States, differences exist in study protocols and especially, project duration, startup difficulties and scavenge and search efficiency calculations. Seasonal patterns of mortality have a strong effect on annual results and comparisons should preferably be made with projects that occurred during the same time of year. The analyses described in this report will provide ample information for designing a fatality study protocol for the coming years. Carcass removal and scavenging rates, combined with other findings, can be used to determine the optimal search interval and sample size of turbines needed to be searched for the entire 195 turbines at the Maple Ridge Wind Power Project.

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