Koffijberg, Kees, Nikolas Prior, Preben Clausen, Kane Brides, Christine Kowallik, Menno Hornman, Koen Devos, et al. “Decline of the Bewick’s Swan Cygnus Columbianus Bewickii Population Wintering in Northeast Northwest Europe”. Wildfowl 75 (December 12, 2025): 63–93. Accessed December 13, 2025. https://tidsskrift.dk/Wildfowl/article/view/162735.