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Behavioral Responses of Bats to Operating Wind Turbines

Wind power is one of the fastest growing sectors of the energy industry. Recent studies have reported large numbers of migratory tree-roosting bats being killed at utility-scale wind power facilities, especially in the eastern United States. We used thermal infrared (TIR) cameras to assess the flight behavior of bats at wind turbines because this technology makes it possible to observe the nocturnal behavior of bats and birds independently of supplemental light sources. We conducted this study at the Mountaineer Wind Energy Center in Tucker County, West Virginia, USA, where hundreds of migratory tree bats have been found injured or dead beneath wind turbines. We recorded nightly 9-hour sessions of TIR video of operating turbines from which we assessed altitude, direction, and types of flight maneuvers of bats, birds, and insects. We observed bats actively foraging near operating turbines, rather than simply passing through turbine sites. Our results indicate that bats: 1) approached both rotating and nonrotating blades, 2) followed or were trapped in blade-tip vortices, 3) investigated the various parts of the turbine with repeated fly-bys, and 4) were struck directly by rotating blades. Blade rotational speed was a significant negative predictor of collisions with turbine blades, suggesting that bats may be at higher risk of fatality on nights with low wind speeds. (Journal of Wildlife Management 72(1):123–132; 2008)

Jason W. Horn, Center for Ecology and Conservation Biology, Department of Biology, Boston University
Edward B. Arnett, Bat Conservation International, Austin, Texas
Thomas H. Kunz, Center for Ecology and Conservation Biology, Department of Biology, Boston University

Download original document: “Behavioral Responses of Bats to Operating Wind Turbines [1]

Twenty-three videos illustrating several aspects (investigating the turbine tower and nacelle, investigating and chasing turbine blades, bat avoidance behavior, contact with blades, birds, multiple bats, and height reference) of bat flight at night around wind turbines are available from Boston University: click here [2].