Pushed by increasing air temperature and tailwind speed: Weather selectivity of raptors migrating across the Aegean Sea

Abstract

A vast number of raptors migrates between the Western Palearctic and Africa every autumn. Species and/or populations of migratory raptors that choose to cross the Mediterranean Sea need to overcome an extended ecological barrier, which is particularly extensive in the area of east-central and east Mediterranean. We tested the selectivity of two raptor species to weather and phenology analyzing the data collected on a small Greek island throughout four different years. Weather selectivity of the two species shows both similarities and differences. The intensity of migration of both studied species is positively correlated with air temperature. The European Honey Buzzard selects days with strong tailwind assistance that helps to reduce flight time over sea thus decreasing mortality risk and energy consumption during this sea crossing. On the other hand, the Western Marsh Harrier seems to be less wind selective reaching the island in good numbers also with headwinds, probably because of its higher ability in using powered-flapping flight.