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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	[Occurence of Common Pochard X Ferruginous Duck hybrids, Aythya ferina X A. nyroca]
Auteurs :	Christoph Randler, Auteur
Type de document :	Article
Dans :	Vogelwarte (40(3) November, 2000)
Article en page(s) :	206-211
Langues:	Allemand
Mots-clés :	Anatidae ; Hybridation
Résumé :	Presumed wild hybrids between the Common Pochard (Aythya ferina) and the Ferruginous Duck (A. nyroca) have been noted in Central Europe first in 1955. Hybridization between these two species is very common and their offspring is said to be fertile. This cross is one of the most common in the Anatidae with about 16% of all crosses recorded. It is only outnumbered by hybrids between Common Pochard X Tufted Duck (A. fuligula), which are by far the most common ones (40%). 147 observations of 157 individuals have been reported between 1962 and 1998. Common Pochard X Ferruginous hybrids were mostly recorded as single ones, these are 95% of all instances. The sex ratio appears very uneven with 3 males: 1 female (total number: 95 males, 34 females). Compared to Common Pochard X Tufted Duck hybrids, the share of females is much lower in the latter cross (3,7%). In the southern parts of Central Europe the seasonal occurrence is one-peaked with highest numbers present in January. The occurrence in Northern Germany looks quite similar, but with a less distinct peak. In both cases it is typical for a winter visitor. Most hybrids were found in western and especially in the southern parts of the study area, e.g. at Lake Constance, the Upper Rhine valley and the Swiss 'Mittelland'. Numbers of hybrids increased steadily since 1978. It is discussed whether this increase is real or artificial. Improved literature of identification is considered as one factor. Decreasing numbers of the breeding population of Ferruginous Duck at the border of its western range make it difficult to find adequate partners to pair-off, so that hybridization with Common Pochards will occur more frequently.

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