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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Hybrids between Pochard Aythya ferina and Tufted Duck A. Fuligula in Germany, Austria and Switzerland
Auteurs :	Christoph Randler, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (120(4) 1999)
Article en page(s) :	211-220
Mots-clés :	Anatidae ; Hybridation
Résumé :	Apparent hybrids between Common Pochard and Tufted Duck have been noted in west-central Europe in the wild since 1934. This analysis is based on 467 observations of 501 such hybrids in Germany, Austria and Switzerland. 94 % of all observations are of single individuals. The seasonal occurrence shows a single peak with highest numbers in December (regions north of 50degree30' N) or January (south of this line; Fig. 2). Between 1950 and 1998, changes in the abundance of these hybrids are apparent (Fig. 3). Prior to the 1980s the average number of observation was 1.6 per year. Between 1982 and 1990 the average number of observations increased about tenfold up to 15.8 each year. From 1991 onwards the numbers rose once again up to 36.2. These changes are thougt to reflect increased observer awareness, mediated mostly by modern identification literature. In 1982 a publication in the widespread, Journal fuer Ornithologie '(SCHERER and HILSBERG 1982) brought this subject to the attention of many observers. The increasing numbers of observations in 1991 are probably caused by the translation of the Macmillan Field Guide into German. The geographic distribution (Fig. 4) is concentrated on the Baltic coast, the surroundings of Berlin, the large lakes in Southern Germany and in some parts of Switzerland. This distribution pattern parallels that of the parental species. But it is also a reflection of the recognition of these hybrids by observers and their interests in the subject. The biased sex ratio (only 3.7 % females) is probably due mostly to the difficulty of identifying female hybrids. However, perhaps female hybrids are indeed rarer in accordance with HALDANE's rule. Some factors facilitating hybridization and some aspects of identification are discussed. In the future, all hybrids should be documented and published by regional organisations.

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