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 swan {Cygnus columbianus columbianus} in flight. UK.

David Kjaer / Two Bewick swans {Cygnus columbianus bewickii} flying with full-moon in sky. UK.

Rolf Nussbaumer / Bronzed cowbird {Molothrus aeneus} chick in nest of Bewick's wren, Texas, USA

Rolf Nussbaumer / Bewick's wren with nest material {Thryomanes bewickii} Texas, USA

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