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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	How do intensity of beech mast and winter temperature influence Nuthatch Sitta europaea population dynamics in the Harz Mountains in the non-breeding season?
Auteurs :	Herwig Zang, Auteur ; Paul Kunze, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (128(1) 2007)
Article en page(s) :	1-6,7-10
Résumé :	The Nuthatch breeds in 14 study areas with nest boxes in beech forests of the Harz Mountains. During the winter Nuthatches sleep in the nest boxes, where they were trapped at night in November and in February from 1982 to 2004 (1680 birds in total). These data are a proper basis to analyse the dynamics of a Nuthatch population in beech forests in the non-breeding season.The number of sleeping birds was strongly fluctuating from year to year, but constant on the average from 1982 to 2004. A ratio of 1: 1 was observed between males and females as well as between breeding birds of the preceding summer and immigrants. The connexions are very complex. The number of the sleeping birds in November increased with the density and the breeding success of the preceding breeding season. The number of immigrants from July to November, mostly young birds, did not depend on the size of the breeding population, the breeding success or the intensity of beech mast. The mortality during the winter was related to the temperature, in the same degree in males and females, but more strongly in immigrants than in breeding birds of the preceding season. Compared to other years, winter mortality was lower in years with strong beech mast, especially in immigrants (young birds). For breeding birds of the preceding season such an influence was not evident.In consideration of the two influential factors - winter temperature and intensity of beech mast - a combined ,,temperature-fructification-index" (,,TF-Wert") was calculated. It could be shown that both factors are acting together in an equivalent way and therefore are regulating the survival and the development of the population in a beech forest. From 1982/83 to 2003/04, both the breeding success and the number of immigrants from November to April have increased. However, an influence of the density in autumn (November) and of the intensity of beech mast was not evident.

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