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Abstract

The status of the Great Northern Diver Gavia immer in Galicia, northwest Spain, is reviewed. Numbers peaked in late autumn and early winter, and again in spring. Post-breeding moult was recorded from November to mid December. Individuals in flight feather moult were recorded between February and March, the rest of the pre-breeding moult extending until the last birds departed around mid May. It is suggested that new birds arrive in the area in early spring to moult, replacing part of the wintering population. The species showed a strong preference for exposed sandy coasts in all seasons, but particularly in late winter and spring. The wintering population declined markedly following the Prestige oil spill in 2002/03 (c. 57% from 2002 to 2005). After 2005 the population returned to previous levels, possibly through immigration of birds from the nearby region of Asturias, where the wintering population collapsed in the same period. The average wintering population (uncorrected for detectability) was 123 birds (95% CI = 76–166), c. 2.5% of the estimated European wintering population.