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

Konstantin Mikhailov / Mule Deer (Odocoileus hemionus columbianus) female running, rear view. Olympic NP, Hurricane Hill, Washington, USA, October 2009.

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

Philippe Clement / The Alaska Range and Wonder Lake with Tundra swans {Cygnus columbianus} Denali NP, Alaska, USA.

Philippe Clement / The Alaska Range and Wonder Lake with Tundra swans {Cygnus columbianus} Denali NP, Alaska, USA.

Nigel Bean / Whistling / Tundra swan {Cynus columbianus} portrait

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.

Jim Brandenburg / Tundra Swan (Cygnus columbianus) trio flying against cloudy sky, Minnesota

Jim Brandenburg / Tundra Swan (Cygnus columbianus) flock taking off from lake, Mattamuskeet National Wildlife Reserve, North Carolina

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

David Welling / Banana Slug on leaf, California, USA

Sumio Harada / Columbian Ground Squirrel (Spermophilus columbianus) carrying nesting materials, Glacier National Park, Montana

Marie Read / Tundra Swans (Cygnus columbianus) flock in flight during winter/spring migration. New York, USA, March.

Donald M. Jones / Tundra Swan (Cygnus columbianus) group flying, Fairfield, Montana

Bryan and Cherry Alexander / Nenets girl with pet Swan cygnet, probably Whistling swan (Cynus columbianus). Nadym Tundra, Yamal, Western Siberia, Russia, 2000. 40 BELOW bookplate.

David Kjaer / White-fronted Goose (Anser albifrons) and a Bewick's Swan (Cygnus columbianus) on water. Gloucestershire, UK, March.

David Kjaer / Bewick's Swan (Cygnus columbianus) fighting on water. Gloucestershire, UK, March.

David Kjaer / Bewick's Swan or Tundra Swan (Cygnus columbianus) fighting by water. Gloucestershire, UK, March.

David Kjaer / Bewick's Swan or Tundra Swan (Cygnus columbianus) fighting by water. Gloucestershire, UK, March.

David Kjaer / Four Bewick's Swan / Tundra Swan (Cygnus columbianus) in flight. Gloucestershire, UK, January.

David Kjaer / Bewick's Swan or Tundra Swan (Cygnus columbianus) fighting on water. Gloucestershire, UK, March.

David Kjaer / Bewick's Swan (Cygnus columbianus) in flight. Gloucestershire, England, January.

David Kjaer / Bewick's Swan or Tundra Swan (Cygnus columbianus) foraging in water. Gloucestershire, UK, March.

David Kjaer / Bewick's Swan (Cygnus columbianus) in flight, one wearing radio transmitter around neck. Gloucestershire, England, January.

Ernie Janes / Flock of Bewick swans (Cygnus columbianus) feeding at dusk in winter, Cambridgeshire, UK,

Kevin Schafer / Banana Slug (Ariolimax columbianus) on trunk of Island Oak (Quercus tomentella), Channel Islands National Park, California

Nature Production / Two Bewick's Swans (Cygnus columbianus bewickii) sleeping with head tucked under wing, Niigata, Japan, January

Diane McAllister / Tundra / Whistling swans (Cygnus columbianus) circling around as they prepare to land on partially frozen Swan Lake. Lemmon Valley, Nevada, USA, December

Diane McAllister / Tundra / Whistling swans (Cygnus columbianus) circling around as they prepare to land on Swan Lake. Lemmon Valley, Nevada, USA, December

Diane McAllister / Tundra / Whistling swans (cygnus columbianus) coming in to land gently onto frozen Swan Lake during the start of a snowstorm. Lemmon Valley, Nevada, USA, December

Diane McAllister / Black-tailed deer (Odocoileus hemionus columbianus), subspecies of the Mule deer. This young buck eating grass pauses to watch the photographer on a trail in Point Reyes National Seashore. California,...

Matthew Maran / Two Blacktail Deer (Odocoileus hemionus columbianus) sparring with locked horns. Ucuelet, Vancouver Island, Canada, September.

Bryan and Cherry Alexander / Nenets girl posing with pet Bewick's swan cygnet (Cygnus columbianus bewicki) at summer camp near Nadym, Yamal, Western Siberia, Russia, 2000.

Bryan and Cherry Alexander / Nenets girl playing with pet Bewick's swan cygnet (Cygnus columbianus bewicki) at summer camp near Nadym. Yamal, Western Siberia, Russia, 2000.

Bryan and Cherry Alexander / Nenets children feeding a pet young Tundra / Bewick's swan (Cygnus columbianus bewicki) at a summer camp near Nadym. Yamal, Western Siberia, Russia, 2000.

Nick Upton / Aerial view of Bewick's swans (Cygnus columbianus) feeding in flooded, partly frozen ploughed field, fenland near Lakenheath, Suffolk, UK, January.

Nick Upton / Aerial view of Bewick's swans (Cygnus columbianus) feeding in flooded, partly frozen ploughed field, fenland near Lakenheath, Suffolk, UK, January.

Mark Carwardine / Bewick's / Tundra swan (Cygnus columbianus bewickii) head portrait, Slimbridge, Gloucestershire, UK, September

Mark Carwardine / Bewick's / Tundra swan (Cygnus columbianus) head portrait, Slimbridge, Gloucestershire, UK, September

Mark Carwardine / Bewick's / Tundra swan (Cygnus columbianus) portrait, Slimbridge, Gloucestershire, UK, September

Mark Carwardine / Bewick's / Tundra swan (Cygnus columbianus) with water dripping from beak, Slimbridge, Gloucestershire, UK, March

Nick Upton / Bewick's swan (Cygnus columbianus bewickii) flying in to evening roost site in warm sunset light, Gloucestershire, UK, March.

Bryan and Cherry Alexander / Nenets girl with pet Reindeer / Caribou calf (Rangifer tarandus) and Swan cygnet, probably Whistling swan (Cynus columbianus). Nadym Tundra, Yamal, Western Siberia, Russia, 2000.

Bryan and Cherry Alexander / Nenets girl with pet Swan cygnet, probably Whistling swan (Cynus columbianus). Nadym Tundra, Yamal, Western Siberia, Russia, 2000.

David Woodfall / Bewick swans (cygnus olor) at Slimbridge Wildfowl and Wetlands Trust, Gloucestershire, England, UK

David Kjaer / Bewick's Swans (Cygnus columbianus) adult with first winter juveniles, Gloucestershire, England

Konstantin Mikhailov / Mule Deer (Odocoileus hemionus columbianus) female standing in grassland, Olympic NP, Hurricane Hill, Washington, USA, October 2009.

David Kjaer / Small flock of Bewick's / Tundra swans (Cygnus columbianus) in flight, Gloucestershire, England

David Kjaer / Small flock of Bewick's / Tundra swans (Cygnus columbianus) in flight over snow covered field, Gloucestershire, England

LYNN M. STONE / Tundra / American whistling swan (Cygnus columbianus) landing on the Mississippi River, Minnesota, USA

Gerrit Vyn / Grizzly Bear (Ursus arctos) scavenging the remains of a dead Tundra Swan (Cygnus columbianus). Seward Peninsula, Alaska, USA, June.

Donald M. Jones / Tundra Swan (Cygnus columbianus) flying, central Montana

Donald M. Jones / Tundra Swan (Cygnus columbianus) flock flying, central Montana

Donald M. Jones / Columbian Ground Squirrel (Spermophilus columbianus), Glacier National Park, Montana

Donald M. Jones / Columbian Ground Squirrel (Spermophilus columbianus) at burrow eating flowers, Glacier National Park, Montana

Donald M. Jones / Columbian Ground Squirrel (Spermophilus columbianus) standing amongst flowers, Glacier National Park, Montana

Steven Kazlowski / Columbian ground squirrel (Spermophilus columbianus) adult foraging for food near Gunsight Lake campground, Glacier National Park, Montana, USA.

Andy Rouse / Two Bewick's swans (Cygnus columbianus) in flight, Welney WWT, Cambs, UK

David Tipling / Bewick's swan (Cygnus columbianus) coming in to land, Slimbridge, Gloucestershire, UK, February

David Tipling / Bewick's swan (Cygnus columbianus) on water, Slimbridge, Gloucestershire, UK, February

David Tipling / Bewick's swan (Cygnus columbianus) in flight, Slimbridge, Gloucestershire, UK, February

David Tipling / Wildfowl including Bewick's swans at dusk in front of buildings, Slimbridge WWT, Gloucestershire, UK, February 2009

Alan Williams / Bewick's swan (Cygnus columbianus) in flight, Welney, WWT, UK, November

Alan Williams / Bewick's swan (Cygnus columbianus) in flight, Welney, WWT, UK, November

Alan Williams / Bewick's swans (Cygnus columbianus) in flight, Welney, WWT, UK, October

Alan Williams / Bewick's swans (Cygnus columbianus) in flight, Welney, WWT, UK, October

Alan Williams / Bewick's swans (Cygnus columbianus) two adults and one juvenile in flight, Welney, WWT, UK, November

Alan Williams / Bewick's swans (Cygnus columbianus) five juveniles with one adult in flight, Welney, WWT, UK, November

Russell Cooper / Bewick's swan (Cygnus columbians bewickii) resting, captive

Donald M. Jones / Red Fox (Vulpes vulpes) female with Columbian Ground Squirrel (Spermophilus columbianus) prey, western Montana

Donald M. Jones / Red Fox (Vulpes vulpes) female with Columbian Ground Squirrel (Spermophilus columbianus) prey, western Montana

Donald M. Jones / Columbian Ground Squirrel (Spermophilus columbianus), western Montana

Donald M. Jones / Columbian Ground Squirrel (Spermophilus columbianus) juveniles at burrow entrance, western Montana

Donald M. Jones / Columbian Ground Squirrel (Spermophilus columbianus) with nose covered with soil, western Montana

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

Steve Knell / Bewick's swan (Cygnus columbianus bewickii) with water droplets dripping from bill after drinking, Slimbridge WWT, Gloucestershire, England, January

Sebastian Kennerknecht / Tundra Swan (Cygnus columbianus) pairs fighting, Tule Lake National Wildlife Refuge, California

Sebastian Kennerknecht / Tundra Swan (Cygnus columbianus) landing, Tule Lake National Wildlife Refuge, California

Sebastian Kennerknecht / Tundra Swan (Cygnus columbianus) pair landing, Tule Lake National Wildlife Refuge, California

Tim Laman / A Bald eagle (Haliaeetus leucocephalus) at the Lower Klamath section of the refuge with Tundra swans / Whistling swans (Cygnus columbianus) in the background. Tule Lake National Wildlife Refuge, Calif...

Tim Laman / Tundra swans / Whistling swans (Cygnus columbianus), ducks and Coots (Fulica atra) with Mt. Shasta at sunrise. Tule Lake National Wildlife Refuge, California. Nov 2002.

Michio Hoshino / Tundra Swan (Cygnus columbianus) flock flying, Alaska

Sumio Harada / Columbian Ground Squirrel (Spermophilus columbianus) feeding on alpine flowers, Rocky Mountains, North America

Mike Potts / Bewick's Swans (Cygnus columbianus bewickii), winter, Ouse Washes, Cambridgeshire, UK February

Mike Potts / Two Bewick's swans (Cygnus columbianus bewickii) flying, Ouse Washes, Cambridgeshire, UK February

Mike Potts / Bewick's swans (Cygnus columbianus bewickii) on water, Ouse washes, Cambridgeshire, UK February

Mike Potts / Bewick's swan (Cygnus columbianus bewickii) in flight, Ouse Washes, Cambridgeshire, UK February

Mike Potts / Bewick's swans (Cygnus columbianus bewickii) flying, Ouse Washes, Cambridgeshire, UK February

Mike Potts / Bewick's swans (Cygnus columbianus), Two adults and one immature (with neck collar) in flight, Ouse Washes, Cambridgeshire, UK February

Mike Potts / Bewick's swans (Cygnus columbianus bewickii) on water, Ouse Washes, Cambridgeshire, UK February