Damian Wiehle
Ornis Polonica 2020, 61: 88–116
https://doi.org/10.12657/ornis.2020.2.2
Abstract: This paper presents current breeding avifauna of the refugium located in the SPA Dolina Dolnej Skawy (PLB120005) in S Poland, and its changes across the last few decades. Dolina Dolnej Skawy hosts 23 bird species associated with fish ponds and former gravel pits. The refugium covers the area of 7,081.88 ha, and is located in Kotlina Oświęcimska (the Oświęcim Basin). In addition to systems of fish ponds, it encompasses a part of the lower Vistula River and its tributary, the Skawa, and some gravel pit reservoirs. The landscape is a forestless mosaic of intensively cultivated agrocenoses and ponds, dotted with villages and suburban infrastructure. The comparison of data from 2008–2018 and 1995–2002 revealed that populations of 28 species decreased or remained unchanged, while populations of 23 species increased between the two periods. The highest increase in population size has been observed for the Caspian Gull Larus cachinnans, the Whiskered Tern Chlidonias hybrida, and the Gadwall Mareca strepera. Seven species no longer regularly nest in the area, i.e. the Red-crested Pochard Netta rufina, Ferruginous Duck Aythya nyroca, Black Tern Ch. niger, Common Gull L. canus, Yellow-legged Gull L. michahellis, Mediterranean Gull Ichthyaetus melanocephalus, Black-tailed Godwit Limosa limosa, and Common Snipe Gallinago gallinago. New species have appeared in the area, including three species nesting regularly (the Goosander Mergus merganser, Common Crane Grus grus, and Grey Wagtail Motacilla cinerea), two species nesting irregularly (the Egyptian Goose Alopochen aegyptiaca and European Bee-eater Merops apiaster), and five species nesting occasionally (the Black-winged Stilt Himantopus himantopus, Purple Heron Ardea purpurea, Little Egret Egretta garzetta, Yellow-legged Gull Larus michahellis and Citrine Wagtail Motacilla citreola). Four factors causing the changes in the breeding avifauna of the refugium can be distinguished. The first factor is the limited production of fish for consumption in key local fisheries (Spytkowice, Przeręb, Bugaj, and Stawy Monowskie), resulting in the limited amount of available food during the breeding period (March–September). The second factor is the mass hunting of birds, which exterminates endangered species and negatively impacts all the protected species, especially Anseriformes, rails, terns and grebes. The third factor is the predation by the Red Fox Vulpes vulpes and the Raccoon Dog Nyctereutes procyonoides. The last factor is climate change resulting in the disappearance of snow cover and hence the shortage of water necessary for filling the ponds in early spring.
Keywords: climate change, collective hunting, fish ponds, population trends, the Vistula and Skawa River, water shortage, waterbirds
