Bird and Bat Fatality Studies Fowler Ridge III Wind-Energy Facility Benton County, Indiana: April 2 - June 10, 2009


Title: Bird and Bat Fatality Studies Fowler Ridge III Wind-Energy Facility Benton County, Indiana: April 2 - June 10, 2009
Publication Date:
April 12, 2010
Pages: 31
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Johnson, G.; Ritzert, M.; Nomani, S.; Bay, K. (2010). Bird and Bat Fatality Studies Fowler Ridge III Wind-Energy Facility Benton County, Indiana: April 2 - June 10, 2009. Report by Western Ecosystems Technology Inc (WEST). pp 31.

BP Wind Energy North America, Inc. (BPWENA) is developing a wind-energy facility in five separate phases for a total build out capacity of 1,000 megawatts (MW) in Benton County, Indiana. Currently, the first three phases have a total energy capacity of 750 MW. The third phase of the facility, Fowler Ridge III, is owned entirely by BPWENA and is located approximately two miles (3.2 km) east of Fowler, Indiana, and consists of 60 Vestas V82 1.65-MW turbines with a nameplate capacity of 99 MW.


BP Wind Energy North America contracted Western Ecosystems Technology, Inc. (WEST) to develop a post-construction fatality monitoring study at the Fowler I and Fowler III facilities to assess the level of impacts to birds and bats (i.e., high, moderate, low) relative to other wind-energy facilities from operation of the Fowler Ridge I and Fowler Ridge III facilities. Monitoring at the Fowler Ridge III Wind-Energy Facility occurred during the spring migration and early breeding season (April 2 through June 10, 2009), while monitoring of the Fowler I Wind-Energy Facility occurred from April 6 to October 30, 2009. This report presents results of monitoring conducted only at the Fowler III Wind-Energy Facility.  Summer and fall migration surveys at the Fowler III Wind-Energy Facility were not conducted due to project-related budget constraints and the expectation that a more robust study would be conducted the second year.


The primary objective of the monitoring study was to determine the level of bird and bat mortality (i.e., relatively high, moderate, or low mortality) attributable to collisions with wind turbines compared to other regional wind-energy facilities. Because not all turbines were sampled, the study was not designed to quantify mortality with a high degree of accuracy for the entire wind energy facility, nor was it designed to detect every wind turbine casualty present on the site.  The monitoring study consisted of four components: 1) standardized carcass surveys of selected turbines; 2) searcher efficiency trials to estimate the percentage of carcasses found by searchers; 3) carcass removal trials to estimate the length of time that a carcass remained in the field for possible detection; and 4) adjusted fatality estimates for birds and bats, calculated using the results from searcher efficiency trials and carcass removal trials, to estimate the approximate level of bird and bat mortality within the Fowler Ridge III Wind-Energy Facility.  


Twenty percent of the available turbines (12 turbines) were scheduled to be searched either weekly or biweekly throughout the monitoring period. Search plots 160 meters (525 feet) on a side were established around each turbine to ensure all areas within 80 meters (262 feet) of a turbine were searched. Most of the turbines were located in corn and soybean fields; however, these crops were either not present or very immature during the time frame of the study (April 2 – June 10) and therefore no clearing of crops was conducted for this study. Surveyors walked parallel transects within the search plots while scanning the ground for fatalities or injured birds or bats.


The objective of the standardized carcass surveys was to systematically search selected turbines for bird and bat casualties attributable to collision with project facilities. During the study, three birds were found. All three of the fatalities were comprised only of a few bones without any feathers or fleshy parts remaining. Two of the fatalities were identifiable only as ducks based on skull characteristics, while the remaining casualty was only identifiable as a large bird because no skull was present; that casualty was likely also a species of waterfowl. No bird fatalities were found incidentally. The FRWEF-III is near an area designated as an Important Bird Area (IBA) due to high concentrations of staging American golden plovers during spring migration. Although concerns have been raised over the potential for collision mortality, no American golden plover fatalities were found during this study.


Two of the bird fatalities (the unidentified large bird and one unidentified duck) were found at Turbine 432 and the remaining unidentified duck casualty was found at Turbine 435. All bird fatalities were found greater than 60 meters (197 feet) from the turbines. 


Five bat fatalities comprised of four species were found, including two hoary bats and one each of the following species: eastern red bat, silver-haired bat, and big brown bat. No bat casualties were found incidentally. Bat fatalities were all found at Turbines 387, 432, 435, 444, and 464. Two of the bat fatalities were found between 10 and 20 meters (33-66 feet) from the turbines, two were found between 40 and 50 meters (131-164 feet) from the turbines, and one was found more than 60 meters (197 feet) from the turbine. Bat fatalities were evenly distributed throughout the duration of the study season. Three bat fatalities were intact, one was scavenged, and one was found alive and was subsequently released.


Pre-construction ground-based bat acoustical surveys were conducted at the Fowler Ridge Wind Resource Area from August 15 – October 19, 2007 and from July 17 – October 15, 2008, time periods that cover the time frame during which most bat mortality at wind energy facilities occurs throughout North America.  Overall bat detections were low to moderate for sites in the Midwest, ranging from 4.7 bat calls/detector-night in 2007 to 6.45 bat calls/detector-night in 2008.  Although none of the bat casualties found at the FRWEF-III in 2009 were high-frequency species (e.g., Myotis spp.), high-frequency bats comprised 49.0% of bat calls in 2007 and 34.2% of bat calls recorded in 2008, suggesting that high frequency species such as Myotis bats may be much less susceptible to turbine collisions.


Searcher efficiency data from the adjacent Fowler Ridge Phase I Wind-Energy Facility were combined with data from this study to increase sample sizes, whereas all carcass removal data for the Fowler Ridge Phase I Wind-Energy Facility were used for this study. For searcher efficiency trials, 16 carcasses (eight large birds and eight small birds) were placed in the field during searcher efficiency trials conducted on two separate dates. Observer detection rates were 83.3% for large birds and 50.0% for small birds. 


For carcass removal trials, 16 carcasses were placed in the Fowler Ridge Phase I Wind-Energy Facility, including eight large bird and eight small birds. By day ten, approximately 25% of the large birds remained, while approximately 35% of the small birds remained.


Because all three birds found during the study were estimated to have died well before the study was initiated, no estimates of avian mortality could be made. The estimated number of bat fatalities and associated 90% confidence limits for the study period from April 2 – June 10 was 3.03 bat fatalities/turbine (90% confidence interval of 0.71 to 6.58 bat fatalities/turbine). Based on the 1.65-megawatt capacity of turbines at the Fowler Ridge Phase III Wind-Energy Facility, the estimated number of bat fatalities was 1.84 bat fatalities per megawatt during the April 2 to June 10 study time period, or a total of 182 estimated bat fatalities for the entire 99-MW facility.


To date there have been fewer than 10 studies conducted to estimate bird and bat fatalities from wind turbine operations in the Midwest, and studies at the Fowler Ridge Wind Energy Facility represent the first such studies in Indiana.   Results of this study further contribute to our understanding of wind-energy impacts to birds and bats. As more wind-energy facilities are built in the region, and additional studies become available, a clearer picture of the impacts to birds and bats will emerge.

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