Bibliothèque Tour du Valat

Se connecter

Mot de passe oublié ?
Pas encore inscrit ?

La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Détail

Ajouter au panier

Ajouter au panier

Lien vers la notice

Titre :	[Wintering Blackcaps Sylvia atricapilla in Denmark.]
Auteurs :	Bo Thyge Johansen, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (96(2) 2002)
Article en page(s) :	67-74
Langues:	Anglais
Résumé :	As in other countries in northern Europe, wintering Blackcaps have have been seen in Denmark in increasing numbers during the last 30 years (Fig. 1). At least 754 Blackcaps have been recorded during the winters 1898/99 - 1996/97, all but 9 of them since 1960, whereas winter records exist for each year since 1964. It seems very likely that the increasing number of field ornithologists during the 20th century, combined with more efficient channels for reporting bird observations, to some extent is responsible for this striking development, but for the major part it must have been caused by a real change in the species' migratory and wintering habits. No clear relationship has been found between the number of Blackcaps recorded in any given winter and either the mean winter temperature or the mean temperature of the preceding November. There is, however, some indication that numbers of wintering Blackcaps are low in years following very cold winters, suggesting that a subpopulation "programmed" for wintering in northern Europe is decimated under extreme winter conditions and builds up gradually during uninterrupted periods of mild winters. Recorded Blackcaps during late autumn and winter, for 1898-1997 combined, are shown in Fig. 2. Numbers fall sharply after the first decade of November, probably because the last autumn migrants then disappear. From December onwards, however, numbers increase again until late February. The reason for this pattern may, at least in part, be that, as the winter progresses, the Blackcaps gradually move to areas such as suburbs where they are likely to be noticed by humans. Of 393 Blackcaps for which the habitat is known, 69% occurred in gardens. Here they foraged on berries or fallen apples and other fruit, and on seed, fat, bread, fruit and other food at bird feeders. A majority of the wintering Blackcaps for which the sex is known were males (60%, n = 492), and this percentage remained constant throughout the winter.

FAQ

Infos pratiques

Heures d'ouverture et contact

Lundi , mardi et jeudi de 9h à 12h et de 13h à 17h00 : ouverture au public ...

Liens utiles

A-
A
A+