David Pattyn / Bewick's swans (Cygnus bewickii) four in flight, Den Bosch, The Netherlands, January

Paul Hobson / Bewick's swan (Cygnus columbianus bewickii) flying across a full moon, UK, February 2011

David Kjaer / Small flock of Bewick's / Tundra swans (Cygnus columbianus) on water, in snow covered landscape, Gloucestershire, England

Steve Knell / Two Bewick's swans (Cygnus columbianus bewickii) in flight, Slimbridge WWT, Gloucestershire, England, January

Steve Knell / Bewick's swan (Cygnus columbianus bewickii) alert on water, Slimbridge WWT, Gloucestershire, England, January

David Tipling / Bewick's swans on water {Cygnus bewickii} WWT Slimbridge, Gloucestershire

David Kjaer / Bewick's swans, silhouette of four flying after sunset {Cygnus bewickii} UK

David Kjaer / Two Bewick's swans in flight {Cygnus bewickii} UK

David Tipling / Bewick's swan {Cygnus bewickii} on water. Slimbridge, UK. Winter Gloucestershire

Chris Packham / Bewicks swans in winter. (Cygnus columbianus bewickii) England Hampshire, UK

WILLIAM OSBORN / Bewicks swan standing on ice portrait (Cygnus columbianus bewickii) UK

Geoff Simpson / Bewick swan on water {Cygnus columbianus bewickii} Washington WWT, Co Durham, UK