Trends in chronic marine oil pollution in Danish waters assessed using 22 years of beached bird surveys.

Beached bird surveys provide an important tool for monitoring the level of oil pollution at sea, which is the most significant observable cause of death for a large number of waterbird species and pose a serious threat to wintering seabird populations. Linear regression analyses of oil rates from the Danish 22 year dataset show a decline in the oil pollution level in offshore areas of the eastern North Sea and Skagerrak and in near-shore parts of the Kattegat; but a worsening in the offshore areas of the Kattegat. These results raise concern for species such as common scoter, velvet scoter, eider and razorbill, for which the Kattegat serves as a globally important wintering area. It is recommended that surveillance for oil spills is intensified in inner Danish waters, and that action is taken to make responses towards offenders faster, and penalties for oil seepage higher.