Wintering ducks in the Czech Republic: changes in their population trends and distribution
The Czech Republic, as an inland Central European country, is not part of the core wintering area for most duck species in the Western Palearctic. Nevertheless, interseasonal changes in numbers and distribution of particular species are recorded, which may reflect climatic fluctuation. Waterbird counts were carried out annually at 48–639 wetland sites in the Czech Republic in 1966–2008, as part of the International Waterbird Census (hereafter IWC). These data were used to assess longterm trends in the number of duck wintering in the Czech Republic for the 15 most abundant species. Increasing trends were found for six species: Wigeon Anas penelope, Mallard Anas platyrhynchos, Pochard Aythya ferina, Tufted Duck Aythya fuligula, Smew Mergus albellus and Goosander Mergus merganser. Teal Anas crecca was the only species found to be declining. Those with stable trends were: Pintail Anas acuta, Scaup Aythya marila, Velvet Scooter Melanitta fusca and Goldeneye Bucephala clangula. No (uncertain) trend was found in least abundant Gadwall Anas strepera, Shoveler Anas clypeata, Red-crested Pochard Netta rufina and Ferruginous Duck Aythya nyroca. Wintering distribution (measured as the ratio of the number of sites occupied by a given species to the total number of sites investigated) increased in six species (Wigeon, Gadwall, Mallard, Red-crested Pochard, Tufted Duck and Goosander) and decreased in two species (Teal and Ferruginous Duck). No significant changes in distribution were found for the seven remaining species. Changes in numbers correlated with changes in distribution in each species. Annual variation in the numbers and distribution of ducks wintering in the Czech Republic were more strongly associated with long-term trends in numbers than with annual variation in climate conditions. Nevertheless, the numbers of wintering birds recorded on standing waters were positively correlated with climatic variables in 10 duck species.
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