Ciaranca, Michael A., Charles C. Allin, and Gwilym S. Jones. 1997. “Mute Swan (Cygnus olor).” The Birds of North America, edited by Paul G. Rodewald. Ithaca: Cornell Lab of Ornithology. Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/mutswa doi: 10.2173/bna.273