Reactions of high-flying bats and birds to wind turbines at night
Ronald Larkin, Illinois Natural History Survey
In North America east of the Rockies several species of common bats are killed in large numbers by large commercial wind turbines, but migrating birds are much less commonly killed. The first studies of their behavior as they approach turbines from a distance at night have now been done by the Illinois Natural History Survey, sponsored by the US Department of Energy. The work has revealed that bats are, at least sometimes, attracted to turbines from a distance of several hundred meters, whereas birds are not attracted and indeed can turn away to avoid turbines. Eyeball judgement and quantified computer analysis agree to a high degree of statistical significance. In the course of the work, we discovered remarkable erratic local flights by the bats including swoops, hovers, and prolonged climbs and descents--seemingly prey-capture and/or social behavior, often at heights of half a mile or more above the ground. This behavior by some widespread Nearctic species was unknown.