Boiko, Dmitrijs, and Hakon Kampe-Persson. “Moult Migration of Latvian Whooper Swans Cygnus Cygnus”. Ornis Fennica 89, no. 4 (December 31, 2012): 273–280. Accessed May 20, 2024. https://ornisfennica.journal.fi/article/view/133815.