Łukasz Ławicki, Sławomir Niedźwiecki, Wojciech Sawicki, Piotr Świętochowski, Artur Goławski, Zbigniew Kasprzykowski, Marcin Urban, Przemysław Wylegała, Paweł Czechowski, Marta Prange, Tomasz Janiszewski, Sebastian Menderski, Wiesław Lenkiewicz, Michał Jantarski
Ornis Polonica 2011, 52: 85–96
https://doi.org/10.12657/ornis.2011.2.1
Abstract: During the country-wide census, 167 White-winged Tern colonies were found in 2010 in Poland, totalling for 11 900–12 200 pairs (about 8% of European population). Main nesting grounds were located in eastern Poland: North Podlasie (8 055–8 155 pairs in 82 colonies), Lubelskie Region (1 503–1 718 pairs in 23 colonies) and Mazowsze Region together with South Podlasie (1 281–1 283 pairs in 28 colonies). Biggest numbers were found in the river valleys: Narew (4 135–4 235 pairs in 33 colonies), Biebrza (4 080 pairs in 51 colonies) and Bug (1 770–1 940 pairs in 31 colonies), which together gathered 83% of the 2010 Polish population. 956–1 021 pairs in 32 colonies nested in western Poland, mainly in the valleys of Warta (437–452 pairs), Bzura (165 pairs) and Noteć (95–105 pairs). 92% of colonies were in the river valleys, while remaining breeding sites were the lakes, dam reservoirs and peatland. The biggest colonies in the valleys of eastern Poland gathered 300–700 pairs. Average number per single the location was 73 pairs. Small (11–50 pairs) and medium (51–100 pairs) colonies predominated (together 71%), while large (>100 pairs, 15%) and very small (1–10 pairs, 14%) colonies were both rare. About a half of White-winged Tern colonies were single-species (53%), but almost equally numerous (47%) were multispecies colonies, where White-winged Tern bred with Black Tern Ch. niger, Whiskered Tern Ch. hybrida, Black-headed Gull Larus ridibundus and Common Tern Sterna hirundo. Exceptionally high number of the of White-winged Tern in 2010 was probably caused by (1) intensive spring migration coupled with (2) common ocurrence of favourable nesting biotopes in the valleys of big rivers due to spring overflows and floods, resulting in a high water line across the breeding season.
