Trends in Abundance of Migrating Raptors at Gibraltar in Spring

Abstract

Raptor migration has been monitored regularly at Gibraltar since the mid-1960s. Long-term trends in abundance of spring migration were investigated for the ten most frequent species, five of which changed significantly in abundance during the study period. Black Kites Milvus migrans, Eurasian Sparrowhawks Accipiter nisus and Booted Eagles Hieraaetus pennatus increased. The trends for these three species correspond with those observed elsewhere in western Europe. European Honey-buzzards Perms apivorus and Common Buzzards Buteo buteo, whose western European populations are described as stable, both decreased. For Common Buzzards at least this discrepancy appears to represent a shift in wintering distribution, possibly as a result of climate change, with populations that wintered formerly in North Africa now wintering closer to their breeding grounds.