Przemysław Wylegała, Andrzej Batycki, Bogdan Rudzionek, Karol Drab, Mariusz Blank, Teresa Blank, Justyna Barteczka, Wiesław Bagiński, Andrzej Konopka
Ornis Polonica 2010, 51: 43–55
https://doi.org/10.12657/ornis.2010.1.4
Abstract: In 2003–2009 censuses of selected bird species were performed in the Noteć River valley along its section between Bydgoszcz and Ujście, the site constituting a Natura 2000 bird refuge of European rank named The Valley of the Middle Noteć River and Bydgoszcz Canal. The Middle Noteć valley belongs to the most important refuges of waders in Poland both due to the fact of its housing numerous breeding populations of some species, e.g. the Corncrake Crex crex (124 males), Curlew Numenius arquata (10–12 pairs) and Bluethroat Luscinia svecica (250–280 pairs), and owing to the occurrence in the area of marked concentrations of birds during the migration and wintering periods, including the Tundra Swan Cygnus columbianus (550–600 inds.), Whooper Swan C. cygnus (700–750), Bean Goose Anser fabalis and White-fronted Goose A. albifrons (jointly up to 20 000), Great White Egret Egretta alba (350–400), White-tailed Eagle Haliaeetus albicilla (70–75 inds), Lapwing Vanellus vanellus (9 000–10 000) and Golden Plover Pluvialis apricaria (5 500–6000). Within this refuge, one of the largest in Poland roost of the Common Cranes Grus grus (up to 6 650 inds.) was observed in autumn, and an exceptionally abundant assemblage of moulting Mute Swans C. olor (up to 2 000). In comparison with 1983–1984, among the 40 species under comparison (the majority linked with marshlands), for 17 an increase in the breeding population was recorded and a decrease for 16. The remaining 7 species did not show any trends in number fluctuations. Such trends followed mostly the environmental changes – decline in the intensity of agricultural use of the valley and its secondary turning into marshland. The highest drop in numbers was observed in birds associated with seasonally flooded marshy meadows (wildfowl and waders) and in species connected with fishponds (grebes, diving ducks Aythya, the Coot Fulica atra and Black-headed Gull Larus ridibundus). The increase in abundance concerned mainly species whose population grows in the whole territory of Poland. Also, a strong growth in the numbers of the Bluethroat was noted.
