The data set is showing moulting areas for sea birds (primary sea ducks) in the Baltic Sea area as polygons used for the BRISK project (Sub-regional risk of spill of oil and hazardous substances in the Baltic Sea, http://www.brisk.helcom.fi/). This dataset has been produced by COWI (http://www.cowi.dk) based on data collected from Denmark, Finland (Copyright: SYKE), Germany, Latvia, Lithuania, Poland, Russia and Sweden. The dataset includes data provided by the BRISK Project Partner organisations from various Baltic Sea countries. The detailed documentation of what partner provided what data is given in the Annex of the document: 70618-3.1.2.2 Data Collection Report. During the summer period when the birds change feathers (moulting time) the birds are particularly vulnerable.