This entry focuses on the Eurasian Bewick’s Swan, the form that migrates to Japan. It is white, with a prominent yellow patch at the base of the bill.
Adults of the Eurasian Bewick’s subspecies are white, with black legs and a black bill that has a clear yellow patch at its base.
Bewick’s swans wintering around the Ouse Washes in eastern England change the fields they use as winter progresses. These birds belong to the Eurasian subspecies, Cygnus columbianus bewickii. They feed on post-harvest remains such as sugar beet and potatoes early in winter and increasingly use autumn- and winter-sown cereals such as wheat later. Surrounding farmland provides feeding habitat for birds roosting on the wetlands.
A 2019 paper analysed field observations from winter 1976–1977 onwards. The mean proportion of observed swans on winter-sown cereal fields rose from about 35% in November to 99% in March. The proportion using post-harvest crop remains fell from about 62% to 1%. The surrounding landscape contained both fields with food left after harvest and fields supporting growing crops. A separate assessment of abdominal profiles indicated that fat reserves increased from November to January and then levelled off.
An extinction-risk assessment has not been added yet.
An international conservation action plan for the north-west European wintering population of Bewick’s swan was adopted in 2012. It called for protecting a chain of breeding, staging and wintering sites and maintaining or restoring aquatic plants through water-level and water-quality management. Measures listed to reduce collision risk included burying power lines along routes between roosts and feeding areas and marking lines around key sites. Phasing out lead shot in feeding areas and lead angling weights was also included to reduce poisoning risk.