© Marcel Burkhardt
Strebel, N. (2016)
Wintering Waterbirds in Switzerland. Results of the Swiss Waterbird Census 2014/2015 and 2015/2016.
Swiss Ornithological Institute, Sempach
Since 1967, waterbirds are systematically counted in Switzerland as part of the International Waterbird Census. The collected data is a valuable base for assessing the situation of the waterbird populations and the importance of sites in Switzerland and at the international level.
Previously, the results of the winter waterbird census were published in annual reports usually around one year after the census. Following the last of these reports (Müller & Keller 2015) reporting on national monitoring programmes was restructured. The main results are integrated in a status report (for the recent update see Sattler et al. 2016). From now on, the detailed results are published in a short summary report with accompanying information on the web as an annex to the status report. As a result of the changes in the reporting cycle we decided not to publish a separate report for the season 2014/2015 but to integrate the results in the present report.
Temperatures in October, November and December 2014 as well as in the first days of January 2015 were above average. With around 483’000 individuals, the total count in November was close to the average of the last ten years (Ø 2006–2015 ≈ 477‘000). The result of the January counts was relatively low (492‘000 ind., Ø 2007–2016 ≈ 514‘000). In 2014, record counts for November were reached by Red-crested Pochard (~41‘000 ind., Ø 1991–2015 ≈ 20‘000), Mute Swan (Cygnus olor, ~7700 ind., Ø 1991–2015 ≈ 6200) and Common Snipe (Gallinago gallinago, ~270 ind., Ø 1996–2015 ≈ 150). The following species reached their highest January counts in 2015: Eurasian Curlew (Numenius arquata, ~1800 ind., Ø 1997–2016 ≈ 910), Common Moorhen (Gallinula chloropus, ~900 ind., Ø 1997–2016 ≈ 720), Ferruginous Duck (Aythya nyroca, 91 ind., Ø 1992–2016 ≈ 39), Egyptian Goose (56 ind., Ø 1992–2016 ≈ 15) and Tundra Swan (Cygnus columbianus, 22 ind., Ø 1997–2016 ≈ 9). Greylag Goose, Common Kingfisher and Great Egret also reached new record counts for winter 2014/2015, but the counts were exceeded in the following winter. November counts for the Lesser Black-backed Gull (Larus fuscus) were the lowest for the last 25 years, only 9 individuals were found (Ø 1991–2015 ≈ 26). The lowest November counts for the last ten years were found for Mallard (~37‘000 ind., Ø 2006–2015 ≈ 45‘000), Gadwall (~5600 ind., Ø 2006–2015 ≈ 11‘000) and Eurasian Teal (Anas crecca, ~2300 ind., Ø 2006–2015 ≈ 7000). Mallard and Eurasian Teal also showed the lowest January counts for the last 25 years with around 45’000 ind. (Mallard, Ø 1992–2016 ≈ 51‘000) and around 3500 ind. (Eurasian Teal, Ø 1992–2016 ≈ 6100).
Switzerland experienced a very dry autumn 2015 leading to exceptionally low water levels. November, December and the first days of January 2016 were much warmer than average. In Winter 2015/2016, the total number of waterbirds in Switzerland (including foreign parts of Lake Geneva and Lake Constance) was generally low. In November 2015, the population size of 464’000 was below the average of the last ten years (Ø 2006–2015 ≈ 477‘000 ind.). The number in January was around 483’000 representing the second-but lowest value within the last 25 years. The main reason for the low numbers is the decrease in wintering population of species that breed in Northern Europe and Russia. Ice cover of water bodies located more in the north or east of Europa is decreasing. This allows the birds to spend the winter closer to their breeding grounds (Lehikoinen et al. 2013). In absolute numbers, the wintering population of Tufted Duck (Aythya fuligula) shows the largest decrease. In the 1990s, November counts of Tufted Duck reached a maximum of around 160’000 individuals, January counts went up to 200’000 individuals. In November 2015, only around 86’000 individuals of the species were found, in January around 105’000. The numbers of wintering Common Goldeneye (Bucephala clangula) are decreasing as well. Between 1980 and 2000, wintering population of the Common Goldeneye was usually above 10’000. In January 2016, a new all-time record low was reached with about 4100 individuals. Common Coot (Fulica atra) also experienced a record low for January, 82’000 individuals of the species were found (Ø 1992–2015 ≈ 105‘000 ind.). The same applies to the Mew Gull (Larus canus) with a January count of only around 1600 individuals (Ø 1992–2015 ≈ 5400 ind.). The lowest January counts for the last ten years were found for Mallard (Anas platyrhynchos, ~46’000 ind., Ø 2007–2016 ≈ 51‘000) and for the Red-breasted Merganser (Mergus serrator, 49 ind., Ø 2007–2016 ≈ 74). In contrast, several species experienced noticeable increases during the last years. A continuous growth of the wintering population was found for the Grey Heron (Ardea cinerea, ~2000 ind. in January 2016, Ø 2007–2016 ≈ 1500) and the Great Egret (Egretta alba, 410 ind. in January 2016, Ø 2007–2016 ≈ 250). Wintering populations of the Greylag Goose (Anser anser), the Ruddy Shelduck (Tadorna ferruginea) and the Egyptian Goose (Alopochen aegyptiaca) also showed marked increases. The local population of these species is mostly or totally descending from individuals introduced by humans. The January total of Greylag Goose was around 1700 individuals in 2016, a marked plus compared to 200–300 Individuals that were usually found in the 1990s. Observations of Ruddy Shelduck were very rare in the 1990s, in contrast 1200 individuals were found in January 2016. The Egyptian Goose was virtually absent in the 1990s, in January 2016 around 50 individuals were found. January record counts for the last 25 years were found for Red-crested Po-chard (Netta rufina, 35‘000 ind., Ø 1992–2016 ≈ 20‘000) and – a bit surprising after the low numbers of January 2015 – for Gadwall (Anas strepera, almost 13‘000 ind., Ø 1992–2016 ≈ 8300). With currently around 5000 individuals, the wintering population of the Black-necked Grebe (Podiceps nigricollis) doubled compared to the 1990s. The Common Kingfisher (Alcedo atthis) reached the highest numbers since it was considered for the waterbird census in winter 1996/1997. Last winter, 610 individuals were found in November, 370 in January. The increase is presumably due to favourable weather conditions in winter, in addition it might reflect the increase in breeding population.
Similarly to previous winters, 60 % of all waterbirds concentrated on Lake Constance and Lake Neuchâtel during the counts in November and January.