La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Phenology of South Norwegian Great Black-backed gulls Larus marinus at Helgoland (German Bight)
Auteurs :	Volker Dierschke, Auteur ; Nils Helge Lorentzen, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (127(1) 2006)
Article en page(s) :	31-36
Résumé :	Based on observations of 55 colour-ringed individuals the occurrence of South Norwegian Great Black-backed Gulls on the island of Helgoland (German Bight) is described. Accordingly, birds marked as chicks along the skerries of Vest-Agder (Southern Norway) appear to be migrants from late August to mid November, with few observations in other seasons. Most individuals stay only for it few days, and only a small fraction was observed in more than one year and for longer than one week, respectively. Compared to the phenology at Helgoland in earlier decades and in adjacent regions, Great Black-backed Gulls seem to be flexible in their seasonal occurrence in the German Bight. This is thought to be caused by variable intensities of fishery, which presents variable foraging conditions (discard) for the gulls.

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