European honey buzzard Pernis apivorus

Abstract

The European honey buzzard (Pernis apivorus) is a medium-sized raptor, summer visitor to Europe and Asia, until Kazakhstan, with wintering grounds located in Sub-Saharan Africa. Having an intermediate morphology between obligate-soaring species and those largely using flapping flight, honey buzzards migrate mostly using thermals and deflection updrafts over land but are also capable to cross large water bodies using long non-stop flapping flights. As a result, this is the commonest species observed at nearly all Western Palearctic watchsites, both at the major bottlenecks, where obligate-soaring migrants converge (e.g. Strait of Gibraltar, Batumi, Eilat), and along minor corridors involving several Mediterranean islands. Several study techniques, ranging from visual and radar observations to ringing and biologging. have been used to study flight parameters and migration pathways sometimes at a fine scale, revealing age-dependent migration behaviours such as differences in pathways used among seasons and shaped by wind regimes, geography and related to time and/or risk minimization strategies. As regards the age-dependent migration behaviour, during their first migration juveniles migrate about two weeks later than adults and generally cannot learn the shortest overland route to cross the Mediterranean Sea by social learning. As a result, they migrate on a broad front, largely drifted by prevailing winds and undertaking the water crossings as soon as they hit the Mediterranean coast. Satellite telemetry devices deployed on adult individuals belonging to multiple populations have shown an extreme flexible migration behaviour between and within populations, with some using the same pathways during both spring and autumn and others performing large scale loop migrations. They exploit the tail support of prevailing winds but sometimes choose to fly in suboptimal weather conditions to follow more direct flyways between wintering and breeding grounds. Future research should determine how maturing honey buzzards learn individual and population-specific loop migration patterns, and quantify migratory connectivity between breeding sites, flyways and non-breeding areas.