Meissner, W. and Ciopcińska, K. 2007. Behaviour of Mute Swans Cygnus olor wintering at a municipal beach in Gdynia, Poland. Ornis Svecica. 17, 3–4 (Oct. 2007), 148–153. DOI:https://doi.org/10.34080/os.v17.22685.