Similar to Bewick's Swans, this species is decidedly larger and has a more extensive yellow patch on
its bill. Unlike Bewick's this patch extends to a point under and beyond the nostril forming a triangle. We found
them to be more common in Hokkaido than in Honshu. At one of the Hokkaido crane reserves they were actively hazed
and chased away ostensibly to avoid being a disease vector which might impact the Red-crowned Cranes. A recent
study confirmed that this species may transmit H5N1 influenza from one part of its range to another (China
to Mongolia) Some authors lump this species with the Trumpeter Swan of North America. Canon PowerShot SX60.Reference:
Carboneras, C. & Kirwan, G.M. (2019). 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 1 April 2019).