Ardea
Official journal of the Netherlands Ornithologists' Union

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Cieślak M. & Kwieciński Z. (2009) Moult and breeding of captive Northern Hawk Owls Surnia ulula. ARDEA 97 (4): 571-579
During 20032007, the moult of four captive Northern Hawk Owls Surnia ulula was studied in Poznań Zoological Garden (Poland). The aviary was under daily observation and all breeding events were recorded. It was recognized that captive conditions differ from that in the wild (food availability, expended energy especially by males, and stress) but the study of captive owls allowed a detailed study of moult in relation to the breeding cycle. Identification of dated moulted feathers enabled us to reconstruct the moult process of primaries, secondaries and rectrices. During this study the four birds had different breeding status experiences: single, paired without breeding, paired with unsuccessful or successful breeding. In nine cases, the moult corresponded to patterns described in literature. In every case all primaries and rectrices were renewed each season. Males started moulting 311 days earlier than females and shed all secondaries every year while females replaced from 50100% of secondaries annually. Rate of moult was related to food consumption but not to ambient temperature. During a successful breeding season, the moult of both sexes was two-phased: a short first phase with low moult intensity lasting until young owlets left the nest box followed by a longer, more intense second phase. Breeding females (egg laying and incubation) moulted a few weeks earlier than non-breeding females. In contrast, breeding and non-breeding males had similar patterns of moulting intensity.


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