Wintering Great Northern Divers Gavia immer off the Mullet Peninsula, Co. Mayo, Ireland

Abstract

The Irish wintering population of Great Northern Divers Gavia immer has been estimated at between 1,000 and 1,500 birds. Four sites qualify as internationally important, i.e. regularly supporting 50 or more birds (> 1% of the estimated west European wintering population), of which the shallow seas around the Mullet Peninsula, Co. Mayo is one, with a five-year mean of 54 birds between 1996/97 and 2000/01. From 2002–10, a single count in flat calm conditions was made each January or February of Great Northern Divers in Blacksod Bay, off the southeast coast of the Mullet Peninsula, and from 2005 similar counts were made in Broadhaven Bay, off the northeast coast; in total, these recorded an average of 98 birds. Additional counts suggested wintering numbers were augmented in spring by moulting birds, and that from late February over 250 may be present in the area. These counts, I-WeBs data, and other incidental records, all suggest that the Irish wintering population of Great Northern Divers exceeds 1,500 birds.