La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Obligate and facultative partial migration in the Blackbird (Turdus merula) and the Greenfinch (Carduelis chloris): Uses and limitations of ringing data
Auteurs :	Iain G. Main, Auteur
Type de document :	Article
Dans :	Vogelwarte (40(4) Dezember, 2000)
Article en page(s) :	286-291
Langues:	Allemand
Résumé :	The feasibility of using ring recovery data to distinguish obligate and facultative partial migration is examined. Possible approaches involve (1) the observation of temporal change in the proportion of migrant individuals, and (2) the identification, from ringing and recovery dates, of individuals which migrate from their breeding areas in some winters only. The first approach is illustrated by the progressive decrease during the twentieth century of the proportion of British Blackbirds (Turdus merula) recovered overseas; in that case only a model-dependent interpretation is possible. The second approach reveals that the seasonal movements of Norwegian Blackbirds to Britain and Ireland are essentially obligate, whereas those of Norwegian Greenfinches (Carduelis chloris) both to Britain and to Denmark are most probably facultative.

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