Michał Polakowski, Monika Broniszewska
Ornis Polonica 2013, 54: 96–108
https://doi.org/10.12657/ornis.2013.2.1
Abstract: The Biebrza Basin is an important stopover and foraging site for waterbirds during spring migration. The aim of this study was to investigate the numbers of 3 species of swans and distribution of their main foraging grounds in this area in 1995–2010. The birds were regularly counted in spring (from the second decade of February to the first decade of May) in 2011 and 2012. In total, 13 significant foraging areas were found, gathering 41–320 swans. Wizna Basin and Lower Basin were the most important areas. The Mute Swan Cygnus olor was the most numerous species. Its spring migration began in February with maximal numbers of individuals recorded in the middle of March; the end of migration was difficult to determine, due to presence of non-breeding individuals. Migration of the Whooper Swan C. cygnus began in the mid-February and lasted until mid-April. Maximum numbers were recorded in the third decade of March. The spring migration of the Bewick’s Swan C. columbianus was shorter and lasted from the early March to the second half of April with the peak number recorded in late March. Flooded meadows represented the most important foraging area for all swans during the spring migration, only Whooper Swans foraged occasionally also in the farmland. The Biebrza Basin is an important stopover site during spring migration for three species of swans in Poland.
Keywords: Biebrza Basin, spring migration, stopover site, swans
