Abstract
An ornithological study was carried out over four spring and four autumn seasons from 1999–2003 on one and a half million migrating waterfowl in southern Kalmar Sound in Sweden. The study was conducted in connection with two groups of offshore wind farms constructed at Utgrunden and Yttre Stengrund, with seven and five wind turbines respectively.
The migration patterns of waterfowl through the Sound and the flocks’ reactions on encountering the wind turbines were studied and documented during periods of good visibility by direct visual observation and by following the flocks with an optical rangefinder. During periods of poor visibility (such as fog or mist, or during the night), and similarly during the day with good visibility, radar films from military surveillance radar were analysed in order to follow the flocks’ flight paths and to document their reactions and behaviour when faced with wind turbines in their migratory path.