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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Phenology and population trends of dabbling ducks (Anas spec.) in Germany during the winter season.
Auteurs :	Johannes Wahl, Auteur ; Christoph Sudfeldt, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (126(1) 2005)
Article en page(s) :	75-91
Résumé :	Since 1966/67 waterbirds have been counted in Germany as part of the International Waterbird Census. These data, collected by mostly volunteer observers, were analysed for seven species of dabbling ducks using data from 35 years up to 2002. As site coverage is best during the midwinter census trend analyses focused on January data. Trends were calculated for three periods: 35, 25 and 10 years. Eurasian Wigeon increased strongly for all three periods except for the North Sea coast in the last ten years, which were influenced by two consecutive cold winters. The increase was greatest during a period of extremely mild winters between the end of the 1980s and the mid 1990s. Changes at the North Sea and the Baltic Sea coast occurred almost in parallel. Gadwall numbers went up as well during all periods considered, with a very pronounced increase in NW Germany since the end of the 1980s. Eurasian Teal numbers increased in the S, fluctuated (with an overall slight increase) in the NW, but decreased in the NE due to a pronounced and ongoing decline since the early 1990s. This may be related to improvement in water quality of rivers in E Germany, where most of wintering Eurasian Teals are found, but more detailed analyses are necessary. The most common dabbling duck, Mallard, declined in most regions and periods. This negative trend is confirmed for S Germany since the early 1980s, while in the NW and NE parts the decline was most pronounced during the last decade. Northern Pintail, which winters only in low numbers and few sites, increased, but especially in the N fluctuated according to winter severity. Garganey, for which only data from W Germany were available, decreased strongly until the mid 1980s, but stabilised or moderately increased afterwards (analysed month: April). Northern Shoveler, which is present during winter only in low numbers, showed an overall I positive trend due to an increase during the first decade, but remained stable or fluctuated since. In all species present in winter, especially in the NW and NE parts, a moderate to strong relationship was found between yearly indices and winter severity.

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