Iceland breeding Whooper Swans winter in the UK and Ireland. Approximately 2000 of these swans migrate annually from Iceland to Scotland, a 700 mile non-stop flight that takes 14 to 15 hours. This is probably the longest non-stop flight of any swan. However, about a quarter of the Icelandic population does not migrate. The population breeding in Iceland has been treated as a slightly smaller subspecies C. c. islandicus, but that designation is no longer considered valid. Sometimes placed in genus Olor, this species is the Eurasian counterpart of the Trumpeter Swan of North America. Both species have a loud bugling call generated by an extra long windpipe which reverberates within their hollow breastbone. Canon SX50 HS PowerShot.
References:
Carboneras, C. & Kirwan, G.M. (2018). Whooper Swan (Cygnus cygnus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52807 on 24 September 2018).
Madge, S. & Burn, H. (1988) Waterfowl. An identification guide to the ducks, geese and swans of the world. Houghton Mufflin, Boston.
Todd, F. (1979). Waterfowl. Ducks, Geese & Swans of the World. Sea World, San Diego.