Bats killed by wind turbines were detected in Sweden in 1999. A pilot study to examine the problem was conducted in 2002 and 2003 to suggest further research, actions, and recommendations. Field studies were focused on causes of fatalities and importance of location in the landscape. Acoustic attraction of bats was studied by experiments but results did not support the hypothesis. Attraction of insects was found to cause concentration of hunting bats. Observations with heat image camera at the towers showed that bats frequently hunted insects close to the rotors. The ground under 160 turbines in the provinces Gotland, Öland, Blekinge and Skåne was searched once for killed bats and birds. The result was 17 bats of 6 species and 33 birds of 17 species. Around half of the bats belonged to resident species, while the rest were migrants. All were in the group aerial hawking bats. Almost one third of the birds were swallows and swifts, species that like bats hunt flying insects. The location of the turbines in the landscape was evidently important for the risk of fatalities. Investigations needed prior to planning and locating turbines are recommended. Further research is suggested on bat migration, flyways, accumulations, and coastal points where bats leave and migrate across the sea. More knowledge is also needed about critical areas for the resident bat fauna. Experiments are suggested to test how modifications of turbines can minimize the attraction of insects.
Wind Turbines and Bats - A Pilot Study
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Ahlén, I. (2003). Wind Turbines and Bats - A Pilot Study. Report by Swedish Energy Agency. pp 5.