Swan

Swans swim over a lake as steam ascends above the water during sunset near the village of Urozhainy, Sovetsky district of Altai region...Swans swim over a lake, with the air temperature at about minus 35 degrees Celsius (minus 31 degrees Fahrenheit) as steam ascends above the water during sunset near the village of Urozhainy, Sovetsky district of Altai region, January 26, 2015. About 600 swans annually migrate to the lake, which is heated by warm springs, where they spend their winter being fed by yagers, which help them to survive the severe cold. Picture taken January 26, 2015. REUTERS/Andrei Kasprishin (RUSSIA - Tags: ANIMALS ENVIRONMENT)

Andrei Kasprishin/Reuters

Swans on a lake near the village of Urozhainy, in the Sovetsky district of the Altai region of Russia. The air temperature is minus 35 degrees Celsius. The swans migrate annually to the lake, which is heated by warm springs, where they spend the winter.

Annual Census Of The Swan Population Takes Place On The Thames...SUNBURY, ENGLAND - JULY 15:  Swans and cygnets are caught, measured, assessed and tagged on the River Thames during the annual Swan Upping ceremony on July 15, 2013 in London, England. Swan Upping is the annual census of the River Thames' swan population is led by David Barber, The Queens Swan Marker, it begins on July 15, 2013 in Sunbury and ends at Abingdon, Oxfordshire on July 19, 2013. The Queen's Swan Marker and the accompanying Swan Uppers of the Vintners' and Dyers' Livery Companies use six traditional Thames rowing skiffs in their five-day journey upstream to ensure that the swan population is maintained.  (Photo by Oli Scarff/Getty Images)

Oli Scarff/Getty

Swans and cygnets are caught, measured, assessed and tagged on the River Thames during Swan Upping on Monday in London. Swan Upping, the annual census of the River Thames’ swan population, is led by David Barber, The Queens Swan Marker. It begins on July 15 in Sunbury and ends at Abingdon, Oxfordshire, on July 19. The Queen’s Swan Marker and the accompanying Swan Uppers of the Vintners’ and Dyers’ Livery Companies use six traditional Thames rowing skiffs in their five-day journey upstream to ensure that the swan population is maintained.