Zbigniew Kasprzykowski, Adam Dmoch, Artur Goławski, Radosław Kozik, Cezary Mitrus
Ornis Polonica 2017, 58: 1–11
https://doi.org/10.12657/ornis.2017.1.0
Abstract: This paper presents the results of waterbird counts performed in lower basins of the Bug (1993, 2011) and the Narew River Valleys (1998–1999, 2015). These sites are recognised as Special Protection Areas under the Birds Directive of Natura 2000 network. Numbers of 21/22 species (in the Narew and Bug River Valley, respectively) declined throughout the study period, of 11species increased in both areas, while 2/1 species did not show any temporal trend. Strong population increase in both areas has been found for the Gadwall Anas strepera, European Crane Grus grus, Mute Swan Cygnus olor and Greylag Goose Anser anser. The most important declines were found in the Narew Valley for the Black-tailed Godwit Limosa limosa, Redshank Tringa totanus, Ringed Plover Charadrius hiaticula, Tufted Duck Aythya fuligula and Common Pochard A. ferina. Opposite trends in the two areas were found for the Eurasian Bittern Botaurus stellaris and Marsh Harrier Circus aeruginosus whose populations increased in the Narew Valley and decreased in the Bug Valley. The most significant declines were found for species associated with riverbeds, meadows and pastures. The least abundant species was the Eurasian Stone-curlew Burhinus oedicnemus, whose confirmed broods were recorded at the end of the 20th century. The majority of species inhabiting old river-beds showed an increasing trend. Trends of most species found in the study areas corresponded with national trends. The most important factors affecting waterbird declines were changes in management of breeding habitats, and the increase in predation and human penetration.
Keywords: abundance trends, Bug river, Narew River, river valleys, waterbirds
