Oliver Hellowell / RF - Robin (Erithacus rubecula) perched on mossy branch, Bishopswood, Somerset, UK. May. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - Robin (Erithacus rubecula) juvenile, perched on branch, Bishopswood, Somerset, UK. May. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - Chaffinch (Fringilla coelebs) male, perched on lichen covered branch, Glencoe, Scotland, UK. October. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - Robin (Erithacus rubecula) perched on on mossy log, Bishopswood, Somerset, UK. April. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - Greenfinch (Chloris chloris) male, perched on mossy log, Bishopswood, Somerset, UK. April. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - European goldfinch (Carduelis carduelis) perched in Apple tree (Malus domestica), Bishopswood, Somerset, UK. April. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - Great spotted woodpecker (Dendrocopos major) juvenile, perched on mossy log, Bishopswood, Somerset, UK. June. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - Blue tit (Cyanistes caeruleus) perched on a bare branch, Bishopswood, Somerset, UK. October. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / RF - Blue tit (Cyanistes caeruleus) perched on a stick in snow, Bishopswood, Somerset, UK. February. Cropped. (This image may be licensed either as rights managed or royalty free.)

Oliver Hellowell / Pheasant (Phasianus colchicus) female, head and shoulder portrait, Bishopswood, Somerset, UK. February.

Oliver Hellowell / Marsh tit (Poecile palustris) perched on metal garden sculpture, Bishopswood, Somerset, UK. January. Cropped.

Oliver Hellowell / Grey heron (Ardea cinerea) standing on wooden fence, Trinity Waters fishery, Bridgwater, Somerset, UK. May. Cropped.

Oliver Hellowell / Grey heron (Ardea cinerea) standing on wooden fence, Trinity Waters fishery, Bridgwater, Somerset, UK. May.

Oliver Hellowell / Bullfinch (Pyrrhula pyrrhula) male, perched on wooden fence post, Bishopswood, Somerset, UK. December. Cropped.

Oliver Hellowell / Starling (Sturnus vulgaris) feeding on fat and seed filled coconut shell bird feeder, Bishopswood, Somerset, UK. March.

Oliver Hellowell / Starling (Sturnus vulgaris) perched on coconut shell bird feeder, Bishopswood, Somerset, UK. February.

Oliver Hellowell / Robin (Erithacus rubecula) perched on fallen apple in snow, Bishopswood, Somerset, UK. January.

Oliver Hellowell / Blue tit (Cyanistes caeruleus) perched on mossy stump, Bishopswood, Somerset, UK. September. Cropped.

Oliver Hellowell / Robin (Erithacus rubecula) perched on mossy log with Bluebells (Hyacinthoides non-scripta) in background, Bishopswood, Somerset, UK. May. Cropped.

Oliver Hellowell / Robins (Erithacus rubecula ) pair perched on mossy log performing courtship display, with Bluebells (Hyacinthoides non-scripta) in background, Bishopswood, Somerset, UK. May. Cropped.

Oliver Hellowell / Blue tit (Cyanistes caeruleus) perched on lichen covered twig, Bishopswood, Somerset, UK. September. Cropped.

Oliver Hellowell / Great tit (Parus major) perched on lichen covered branch, Bishopswood, Somerset, UK. April. Cropped.

Oliver Hellowell / Marsh tit (Poecile palustris) perched on Flowering currant (Ribes sanguineum) stem, Bishopswood, Somerset, UK. April. Cropped.

Oliver Hellowell / Blue tit (Cyanistes caeruleus) perched on bird feeder, Bishopswood, Somerset, UK. October. Cropped.

Oliver Hellowell / Blue tit (Cyanistes caeruleus) perched on bare branch, Bishopswood, Somerset, UK. October. Cropped.

Oliver Hellowell / Fieldfare (Turdus pilaris) with puffed up feathers, perched in tree in snow, Bishopswood, Somerset, UK. February. Cropped.

Oliver Hellowell / European robin (Erithacus rubecula) standing in snow, Bishopswood, Somerset, UK. February. Cropped.

Oliver Hellowell / Marsh tit (Poecile palustris) perched on rotten log, Bishopswood, Somerset, UK. September. Cropped.

Jack Dykinga / Sandhill cranes (Grus canadensis) flock in flight with legs extended for landing, Bosque del Apache National Wildlife Refuge, New Mexico, USA. November.

Jack Dykinga / Sandhill cranes (Grus Canadensis) flock in flight at sunset with mountains in background, San Bernadino State Wildlife Refuge, New Mexico, USA. January.

Jack Dykinga / California condor (Gymnogyps californianus) taking flight, Marble Canyon, above the Colorado River, Arizona, USA. February. Critically endangered.

Jack Dykinga / Sandhill cranes (Grus Canadensis) migrating flock in flight at sunset against the rising moon, Whitewater Draw, Arizona, USA. October.

Jack Dykinga / Sandhill crane (Grus canadensis) with Gopher (Geomyida) prey in beak, surrounded by flock of Snow geese (Anser caerulescens) among corn field stubble, Bosque del Apache Refuge, New Mexico, USA. Novemb...

Jack Dykinga / Sandhill crane (Grus Canadensis) taking flight from ice-covered pond, Bosque del Apache National Wildlife Refuge, New Mexico, USA. January.

Jack Dykinga / Greater flamingo (Phoenicopterus ruber) taking flight from river, Ria Celestun Biosphere Reserve, Yucatan state, Mexico.

Jack Dykinga / Greater flamingo (Phoenicopterus ruber) taking flight from river, Ria Celestun Biosphere Reserve, Yucatan state, Mexico.

Tim Laman / Little blue heron (Egretta caerulea) juvenile, perched among a wall of Red mangroves (Rhizophora mangle) in early morning light, at the edge of a lagoon in Caroni Swamp, Trinidad and Tobago.

TOM MANGELSEN / Antarctic fur seal (Arctocephalus gazella) and King penguin (Aptenodytes patagonicus) squabbling, face to face, on beach, Salisbury Plain, South Georgia, South Atlantic Ocean.

Manuel Gracia / European roller (Coracias garrulus) pair mating. Then the birds fly out of the frame briefly and one returns to the perch. Seville, Spain. (Sequence 2/2).

Manuel Gracia / European roller (Coracias garrulus) pair performing courtship feeding ritual and then mating. The male enters frame and presents an insect, the female takes the food and then they mate. After mating,...

Manuel Gracia / European roller (Coracias garrulus) pair performing courtship feeding ritual and then mating. The female enters frame and then calls to her mate. The male lands on the perch and presents an insect, sh...

Manuel Gracia / Close up of European roller (Coracias garrulus) pair performing courtship feeding ritual and then mating. The male enters frame and presents an insect, the female takes the food and then they mate. A...

Manuel Gracia / Close up of European roller (Coracias garrulus) female perched, holding an insect in her beak. The bird looks around and then flies out of frame. Seville, Spain. (Sequence 2/2).

Manuel Gracia / European roller (Coracias garrulus) pair performing courtship feeding ritual. The male is perched and the female lands on perch with food and then the male tries to take food from female. Seville, Spa...

Manuel Gracia / European roller (Coracias garrulus) perched on a branch. Another Roller enters the frame and lands on the same perch. The birds call and display to each other and then they're attacked by a Common kes...

Manuel Gracia / European roller (Coracias garrulus) males fighting over territory and female. The males roll off the hillside and out of the frame. Seville, Spain.

Manuel Gracia / European roller (Coracias garrulus) males violently fighting on a hillside. The birds peck at each other and continue to roll down the hill. Seville, Spain.

Manuel Gracia / European roller (Coracias garrulus) males fighting violently on a hillside. The birds' beaks are locked with one another. Seville, Spain.

Manuel Gracia / European rollers (Coracias garrulus) perched. Another bird enters frame and lands on the perch with others. Then the animals fight, over the nest, leaving the frame briefly. Seville, Spain.

Manuel Gracia / European roller (Coracias garrulus) enters the frame and lands on the perch. Another roller continuously attacks the perched bird, causing it to flee. The bird leaves the frame briefly and then return...

Manuel Gracia / European roller (Coracias garrulus) perched which attacks another roller as it lands on the perch, Seville, Spain.

Manuel Gracia / European roller (Coracias garrulus) pair perched. One bird flies into the nest hole briefly and then returns to the perch. The pair call to each other. Seville, Spain.

Manuel Gracia / European roller (Coracias garrulus) perched. The bird calls and then flies out of the frame. Seville, Spain.

Manuel Gracia / European roller (Coracias garrulus) lands near the nest of another roller. The bird flies out of the nest hole and attacks the perched bird. Seville, Spain.

Manuel Gracia / European roller (Coracias garrulus) pair leaving the nest hole. They fly out of nest hole one after the other. Seville, Spain.

Sylvain Cordier / Common pheasant (Phasianus colchicus) male, walking on dry ground, Penalajo, Castilla, Spain. February.

Sylvain Cordier / Iberian green woodpecker (Picus sharpei) standing on dry ground with legs apart, Sierra de Andujar Natural Park, Andalusia, Spain. February.

Sylvain Cordier / Red partridge (Alectoris rufa) walking over dry ground, Penalajo, Castilla, Spain. February.

Sylvain Cordier / Red kite (Milvus ilvus) perched on a stump, Penalajo, Castilla, Spain. February.

Sylvain Cordier / RF - Red partridge (Alectoris rufa) walking over dry ground, Penalajo, Castilla, Spain. February. (This image may be licensed either as rights managed or royalty free.)

Sylvain Cordier / Red partridge (Alectoris rufa) walking over dry ground, Penalajo, Castilla, Spain. February.

Sylvain Cordier / Red partridge (Alectoris rufa) walking over dry ground, Penalajo, Castilla, Spain. February.

Sylvain Cordier / Three Iberian magpies (Cyanopica cooki) perched on a tree stump, Sierra de Andujar Natural Park, Andalusia, Spain. February.

Sylvain Cordier / European magpie (Pica pica) standing on dry ground, Penalajo, Castilla, Spain. February.

Roger Powell / Common chiffchaff (Phylloscopus collybita) perched on a reed stem over water, Riet Vell Reserve, Ebro Delta Reserve, Catalonia, Spain. January.

David Pike / Greater roadrunner (Geococcyx californianus) walking over dry ground, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Greater roadrunner (Geococcyx californianus) walking over dry ground, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Curve-billed thrasher (Toxostoma curvirostre) standing at edge of pool, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / White tipped dove (Leptotila verreaux) walking along edge of pool, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Curve-billed thrasher (Toxostoma curvirostre) drinking at edge of pool, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Audubon's oriole (Icterus graduacauda) perched in treetop, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Curve-billed thrasher (Toxostoma curvirostre) standing on dry ground, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Audubon's oriole (Icterus graduacauda) taking flight from branch, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Curve-billed thrasher (Toxostoma curvirostre) running over dry ground, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Curve-billed thrasher (Toxostoma curvirostre) running over dry ground, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Northern cardinal (Cardinalis cardinalis) male, standing at edge of pool, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Northern cardinal (Cardinalis cardinalis) female, drinking at edge of pool, Santa Clara Ranch, near Edinburg, Texas, USA. January.

David Pike / Green jay (Cyanocorax yncas) landing on a branch, Santa Clara Ranch, near Edinburg, Texas, USA. January.

Roger Powell / Western marsh harrier (Circus aeruginosus) female, hunting in reed beds, Riet Vell Reserve, Ebro Delta Reserve, Catalonia, Spain. January.

Roger Powell / Western marsh harrier (Circus aeruginosus) female, hunting in reed beds, Riet Vell Reserve, Ebro Delta Reserve, Catalonia, Spain. January.

Roger Powell / Western marsh harrier (Circus aeruginosus) female, hunting in reed beds, Riet Vell Reserve, Ebro Delta Reserve, Catalonia, Spain. January.

Roger Powell / Four Greylag geese (Anser anser) flying low over water, East Chevington Reserve, Druridge Bay, Northumberland, UK. November.

Roger Powell / Greater flamingo (Phoenicopterus roseus) flock flying out from evening roost, La Tancada, Ebro Delta Reserve, Catalonia, Spain. January.

Roger Powell / Greater flamingo (Phoenicopterus roseus) flock flying out from evening roost, La Tancada, Ebro Delta Reserve, Catalonia, Spain. January.

Roger Powell / Greater flamingo (Phoenicopterus roseus) male, wading in shallow water at dawn, La Tancada, Ebro Delta Reserve, Catalonia, Spain. January.

Roger Powell / Great white egret (Ardea alba) male, fishing in shallow water, La Tancada salinas, Ebro Delta Reserve, Catalonia, Spain. January.

Roger Powell / Common kestrel (Falco tinnunculus) female, perched on a nature reserve signpost, looking back, La Tancada, Ebro Delta Reserve, Catalonia, Spain

Nick Upton / Magpie (Pica pica) standing on heavily frosted grass and looking around, Gloucestershire, UK, December.

Nick Upton / Little grebe (Tachybaptus ruficollis) swimming with Caddis fly (Trichoptera sp.) larvae in beak, marshland pool, Magor Marsh nature reserve, Gwent Levels, Wales, UK, March.

Nick Upton / Magpie (Pica pica) foraging in heavily frosted grass, Gloucestershire, UK, December.

Nick Upton / Long-tailed tit (Aegithalos caudatus) foraging perched on English Oak (Quercus robur), Forest of Dean, Gloucestershire, UK, December.

Nick Upton / Lapwing (Vanellus vanellus) flock flying over Greylag geese (Anser anser) foraging and resting on frosted coastal marshland, Severn Estuary, Somerset, December.

Nick Upton / Goosander (Mergus merganser) female taking flight from River Wye, Forest of Dean, Gloucestershire, UK, October.

Nick Upton / Gadwall (Anas strepera) male courting two females, Magor Marsh nature reserve, Gwent Levels, Wales, UK, March.

Nick Upton / Gadwall (Anas strepera) male swimming, Magor Marsh nature reserve, Gwent Levels, Wales, UK, March.

Nick Upton / Common crane (Grus grus) juvenile walking through marshland plants, Slimbridge, Gloucestershire, UK, August.