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Thomas Ruckli

Bestände und Trends überwinternder Wasservögel im Gebiet des Bernauer Staus am Hochrhein seit 1967.

2023

120

64–75

Key words
(von 1994 bis 2006 vergeben)

Wintergäste, Klimaerwärmung, Bestandsrückgang, Wandermuschel, Armleuchteralgen, Eutrophierung

Schlagwort_Vogelart
(wissenschaftlich)

Cygnus olor, Aythya fuligula, Aythya ferina, Anas platyrhynchos, Fulica atra, Larus ridibundus

Schlagwort_Vogelart
(deutsch)

Höckerschwan, Reiherente, Tafelente, Stockente, Blässhuhn, Lachmöwe

Bernauer Stau, Aargau

deutsch

Abhandlung

Populations and trends of wintering waterbirds in the area of the Bernau dam at the High Rhine since 1967. – Since 1967, 40 waterbird species have been recorded in the area of the Bernau dam (canton of Aargau, Switzerland, and Baden-Württemberg, Germany), a reservoir of the High Rhine. Waterbird populations have decreased slightly in November 1991–2021 and considerably in January 1967–2021. Compared to the peak in January 1969 with 2880 individuals, only 952 individuals were recorded in January 2021. The average decline from 1967 to 2021 is around 63%. Also the overall trend in Switzerland has been negative over the last 20 years. One of the main reasons for this decline is climate warming, which reduces the influx of winter visitors, as the birds can winter further north. Yet the decline in the area of the Bernau dam is considerably more pronounced than nationwide. Reasons for this development are the increasing relative attractiveness of lakes, likely combined with a shift of the locally available food supply and an increase of recreational activities on site. For some species, such as the Black-headed Gull Larus ridibundus, the negative trend is also likely to be related to population declines in Europe. Of the species studied in more detail, only Mute Swan Cygnus olor and Mallard Anas platyrhynchos show positive trends in November at Bernau dam (their trends are, however, negative in January). The populations of Tufted Duck Aythya fuligula, Common Pochard A. ferina, Common Coot Fulica atra and Black-headed Gull Larus ridibundus decrease both in November and January.