South West Georgia: an important bottleneck for raptor migration during autumn

Counts of migrating raptors at Batumi, Georgia, revealed the eastern Black Sea coast to form one of the most important bottlenecks for raptor migration during autumn in the Eurasian-African migration system. Totals for 10 species (European Honey-buzzard Pernis apivorus, Steppe Buzzard Buteo buteo vulpinus, Black Kite Milvus migrans, Eurasian Sparrowhawk Accipiter nisus, Levant Sparrowhawk Accipiter brevipes, Montagu's Harrier Circus pygargus, Pallid Harrier Circus macrourus, Lesser Spotted Eagle Aquila pomarina, Greater Spotted Eagle Aquila clanga, Booted Eagle Aquila pennata) exceeded 1% of their estimated world population. We compare the observed abundance of each species to estimates of the presumed source populations in European Russia. Counts of most species involved only a limited subset of these source populations, except for European Honey-buzzard and Lesser Spotted Eagle, which were more numerous than predicted. This could be due to inaccurate population estimates or because birds from NE Europe or W Asia are also using this migration route.