Ostapenko VA. Migration of Bewick’s Swans Cygnus bewickii and Whooper Swans C. cygnus wintering in Japan through Sakhalin Island and adjacent territories, USSR. Wildfowl [Internet]. 2013 Apr. 16 [cited 2025 Dec. 17];:224-6. Available from: https://tidsskrift.dk/Wildfowl/article/view/154979