This is an excerpt from EERE Network News, a weekly electronic newsletter.

June 15, 2005

Report on Bat Mortality at Wind Plants Yields New Insights

The Bat and Wind Energy Cooperative (BWEC) released its 2004 report on bat interactions with wind turbines in early June. The peer-reviewed study involved daily and weekly searches for bat carcasses at wind power sites in Pennsylvania and West Virginia from July 31st to September 13th of 2004. In addition, thermal imaging cameras were used to study bat, bird, and insect activity at the West Virginia site for most of August.

The study found a total of 765 dead bats at the two sites, but estimated the total number of bat fatalities at between 1,764 and 2,900 for the six-week period. None of the bat species found are listed as threatened or endangered. The study found that most of the bats were killed on low-wind nights, when power production was minimal but the blades were turning near their maximum speed. Bat fatalities increased just before and after the passage of storm fronts, and bat activity was highest in the first two hours after sunset. The presence or absence of aircraft warning beacons on the wind turbines did not affect the results. The researchers recommended that future studies be conducted over the entire season of bat movement and activity, namely April through October, to further study these correlations and to help determine "high-risk" times that may be used to mitigate the impacts of wind turbines on bat populations.

BWEC was formed in late 2003 by the American Wind Energy Association, Bat Conservation International, DOE's National Renewable Energy Laboratory, and the U.S. Fish and Wildlife Service. Based on the 2004 findings, the BWEC scientists recommended studying the effects of "feathering" wind turbines during low winds to cut their speeds, but no wind project owner has been willing to conduct such experiments. The BWEC also plans to test the reliability of acoustic detectors at wind power sites and to evaluate the potential for using alerting or deterring devices at wind power sites. See the full report, a summary of findings from the report, and a joint BWEC statement on the report on the BWEC Web site.