The 'chaotic' flight feather moult of the Steppe Buzzard Buteo buteo vulpinus

Steppe Buzzards breed in Eurasia and spend the non-breeding season in Afric a. Adults moult some flight feathers during the breeding season and some du ring the non-breeding season. Moult is arrested during migration. The exten t of moult of flight feathers ill adults is highly variable between individ uals in southern Africa, with the renewal of two primaries, three secondari es and five rectrices as the most frequently encountered pattern. Time spen t on the non-breeding grounds in South Africa is too short to allow for a s equential moult. Moult of flight feathers is restricted to the almost synch ronous dropping of a number of feathers upon arrival, with few being replac ed subsequently. Ally of the flight feathers can be replaced ill southern A frica, and the pattern of renewal ill primaries and secondaries cannot be d istinguished from random. Tail feathers are replaced ill an alternating (tr ansilient) pattern. Moult in the non-breeding areas may primarily be comple mentary to moult on the breeding grounds, but these two partial moults per year are insufficient to renew all flight feathers annually. Middle seconda ries and central tail feathers are regularly carried over to a third moult, but this is rare for primaries.