Wiesław Lenkiewicz, Beata Orłowska, Tadeusz Stawarczyk, Grzegorz Neubauer, Bartosz Smyk
Ornis Polonica 2021, 62: 259–292
https://doi.org/10.12657/ornis.2021.4.1
Abstract: This paper presents changes in the breeding avifauna of the Barycz Valley recorded during last 25–30 years. Temporal trends for 19 bird species nesting at Milicz fish-ponds, the largest Polish fish-pond complex (ca. 6,500 ha), were presented. Among well-studied species, the increasing trend was recorded for 15 species, a declining trend for 13 species, while numbers of 4 species fluctuated without any clear trend. Eight species rarely nested in the valley. The strongest increasing trends were found for the Whooper Swan Cygnus cygnus, Ferruginous Duck Aythya nyroca and Whiskered Tern Chlidonias hybrida, whose local populations are important on the national level (they constitute, respectively, 20.5%, 29.7% and 23.5% of the Polish population). Populations of two species – the Common Tern Sterna hirundo and the Red-necked Grebe Podiceps grisegena, constituted ca. 10% of the national population, whereas in 8 other species the shares made up 5–10% of the national population. Among species with a declining trend two groups can be distinguished. The drop in the number of species associated with reedbeds, like Eurasian Bittern Botaurus stellaris, Marsh Harrier Circus aeruginosus, Eurasian Coot Fulica atra and Little Crake Zapornia parva, probably results mainly from the increasing pressure of mammalian predators – American Mink Mustela vison, Raccoon Dog Nyctereutes procyonoides, Eurasian Red Fox Vulpes vulpes, Eurasian Otter Lutra lutra, and recently also Common Raccoon Procyon lotor, but also from the degradation of some reedbeds. The second group with a declining trend includes birds associated with wetlands, such as the Corncrake Crex crex, Meadow Pipit Anthus pratensis, Thrush Nightingale Luscinia luscinia, Common Rosefinch Carpodacus erythrinus, whose habitats have been dried out. The overall outcome is, however, positive, as the numbers of species with increasing trends exceed the ones with a declining trend. Furthermore, some species with declining trends in Poland, still have strong and stable populations in the Barycz Valley (Common Tern, Red-necked Grebe).
Keywords: Barycz Valley, long-term population trends, Milicz fish-ponds, waterbirds
