The utility of national ring recoveries for identifying the effects of an exceptional mortality event amongst seabirds.

Abstract

Ring recovery data were used to describe a seabird mortality event (or 'wreck') affecting mainly Shags Phalacrocorax aristotelis and Guillemots Uria aalge in the North Sea during February and March 1994. Stormy weather and onshore winds are thought to have caused this mortality. Most Shags and Guillemots were recovered along the North Sea coast of the British Isles, particularly around northeast Britain. In non-wreck years, recoveries of Shags and Guillemots were more widespread around the British Isles. Most Shags recovered during the wreck originated from North Sea breeding colonies in northeast England, eastern Scotland and the Northern Isles, while most Guillemots originated from colonies in eastern Scotland and the Northern Isles. In contrast to previous wrecks, the 1994 wreck affected mainly adult Shags and first- and second-year Guillemots. The national ring recoveries confirmed the extensive scale differences in mortality between species and age classes that were previously evident from an intensive study on the Isle of May.