La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Sex differences in winter distribution of Long-eared Owls (Asio otus) in Denmark and neighbouring countries
Auteurs :	Johannes Erritzoe, Auteur ; Richard Fuller, Auteur
Type de document :	Article
Dans :	Vogelwarte (40(1-2) Oct., 1999)
Article en page(s) :	80-87
Langues:	Allemand
Résumé :	Evidence presented here indicates that in western Denmark, the sex-ratio of Long-eared Owls (Asio otus) during the winter months is significantly biased towards females. Museum collections revealed the same phenomenon in the Netherlands and northern Germany, while sex-ratios approached parity in eastern Denmark. Sweden and central and southern Germany. From the literature, it is clear that there is also a significant winter surplus of females in England, Scotland and the Shetland Islands. Present hypotheses for differential migration are reviewed and it is concluded that none explains adequately this pattern. An alternative hypothesis is presented here, in which heavy predation pressure by Eagle Owls (Bubo bubo) and Goshawks (Accipiter gentilis) on the breeding range in Fenno-Scandia and parts of the Long-eared Owl's wintering range in northern and western Europe is the primary cause of the differential in the observed pattern of winter distribution.

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