Common Scoters breed in freshwater areas throughout northern Europe and Russia, and winter largely in European coastal waters.

In Dutch waters, Common Scoters are usually found north of the eastern Wadden Islands, and to a lesser extent off the coast of the delta. In some years, however, large concentrations have been observed elsewhere. Until now, it was not clear what caused these changes.

In 2016/17, large numbers of Common Scoters were observed off the coast of North Holland. Bureau Waardenburg, on behalf of Rijkswaterstaat, investigated whether prey availability influence their occurrence. This was done in collaboration with Wageningen Marine Research and Altenburg & Wymenga. The results of this study are published in Limosa (Fijn et al. 2017): a PDF of this article can be requested via the email address below.

Results

Common Scoters are benthic specialists, foraging on various types of shellfish that are found on the seabed. The locations of Common Scoters were identified by aerial surveys. The distribution of Common Scoters was compared with that of their prey species.

The study revealed that the high concentrations of Common Scoters could be explained by the availability of food (see figure below), with other factors, such as shipping, likely playing a less important role.

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