Novem (Netherlands Organisation for Energy and Environment) wishes to advance the development of wind energy in the North Sea. As a result of this plan there is a need for knowledge on the effects of wind turbines on birds in nearshore and offshore situations. One of the gaps in knowledge concerns the diurnal and nocturnal flight activity of wintering sea ducks in the vicinity of turbines.
Since there is no offshore windfarm in the Netherlands, a study on this subject was not possible in the Dutch part of the North Sea. In Denmark, however, a windfarm (Tunø Knob) was built in 1994, 7 km offshore in the Kattegat. Large numbers of Eiders and small numbers of Common Scoters spend the winter in the vicinity of this windfarm. A study of potential disturbance effects of this windfarm was undertaken by researchers of the Danish National Environmental Research Institute (NERI, Guillemette et al. 1998). This study comprised only the daylight period. As collision risks are largest in twilight and darkness, Bureau Waardenburg and the Institute for Forestry and Nature Research (IBNDLO), in close co-operation with NERI, conducted a study into the nocturnal flight activity of sea ducks near this windfarm in the winter of 1998/1999.