Post-fledging dependence period and maturation of flight skills in the Black Kite Milvus migrans

Abstract

The post-fledging dependence period of 15 radio-tagged juvenile Black Kites Milvus migrans, was studied in the Donana Biological Reserve (Spain). The juveniles fledged at a mean age of 48 days after hatching and continued to depend on their parents for 15–¸36 days more. During the whole period a progression was observed in the flight behaviour of the young, as an increase of both the total time spent flying and the use of more elaborate and energy-saving flight types such as gliding and soaring. Neither hunting nor manipulative play behaviour with objects was observed, although pursuits were recorded and considered as social play. Migratory restlessness seems to shorten the post-fledging dependence period as the season progresses. Juvenile departure was sudden and definitive, and family ties always broke before migration