Beekman, J., Koffijberg, K., Wahl, J., Kowallik, C., Hall, C., Devos, K., … Rees, E. C. (2019). Long-term population trends and shifts in distribution of Bewick’s Swans Cygnus columbianus bewickii wintering in northwest Europe. Wildfowl, 73–102. Retrieved from https://tidsskrift.dk/Wildfowl/article/view/154488