Loop migration of adult European Honey Buzzards (Pernis apivorus Linnaeus, 1758) through the Central-Eastern Mediterranean

This study provides the first systematic survey of spring and autumn migration of adult European Honey Buzzards (Pernis apivorus) along the Central-Eastern Mediterranean flyway. Observations were done in 2007 and 2008 over the island of Antikythira (southern Greece), located 33 km NW of Crete. A total of 135 birds were counted during spring, 101 in 2007 and 34 in 2008. During post-reproductive movements, the passage of 2479 individuals was reported, 1131 in 2007 and 1348 in 2008. During both years an evident peak during the last ten-days of August occurred. These results clearly show differential spring and autumn migration of adult European Honey Buzzards through this region. Historical data concerning prevailing winds were used to reconstruct general wind patterns in the Central-Eastern Mediterranean region. It showed north-northwesterly winds between southern Greece and Libya during both spring and autumn, but very weak (<10 km/h) during the first period. We discuss two hypotheses to explain why the spring visible migration was so scarce: 1) a narrow migratory loop, with the European Honey Buzzards using a direct path between Libya and Peloponnesus during spring, bypassing Antikythira, and 2) a loop migration on a greater scale, involving a detour via the Bosphorus/Dardanelles' Strait and/or the Central Mediterranean, that would allow the European Honey Buzzards to minimise the water crossing but increasing the overall migration distance. In the light of previous studies on this species, the first hypothesis seems to be much more reliable than the second one.