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) males fighting violently on a hillside. The birds' beaks are locked with one another. 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) pair leaving the nest hole. They fly out of nest hole one after the other. Seville, Spain.

Jabruson Motion / Eastern mountain gorilla (Gorilla beringei beringei) juveniles playing. One juvenile is swinging on a vine and then the other animal pulls them off it and onto the ground. Virunga National Park, Democ...

Neil Aldridge / African lion (Panthera leo) females greeting each other by rubbing their heads together. One animal walks out of the frame. Khwai, Okavango Delta, Botswana.

Neil Aldridge / African lion (Panthera leo) cubs play-fighting. One cub stands up and starts walking away while the other cub chases. Okavango Delta, Botswana.

Tui De Roy / Two Galapagos sea lions (Zalophus wollebaeki) cavorting underwater, with one holding Sea cucumber (Holothuroidea) in mouth. Galapagos Islands, Ecuador. Pacific Ocean.

Juergen Freund / Australian king parrot (Alisterus scapularis) flock entering frame and flying through rainforest, landing on branch and one taking off and leaving frame, Atherton Tablelands, Queensland, Australia.

Juergen Freund / Australian king parrot (Alisterus scapularis) flock entering frame, landing on branch with Australian brushturkey (Alectura lathami) perched on it, before taking flight and leaving frame, with one bir...

Joel Sartore / Photo Ark / One-toed amphiuma (Amphiuma pholeter) head portrait, Oklahoma Aquarium, USA. Captive.

Joel Sartore / Photo Ark / One-toed amphiuma (Amphiuma pholeter) portrait, Oklahoma Aquarium, USA. Captive.

Joel Sartore / Photo Ark / One-toed amphiuma (Amphiuma pholeter) portrait, Oklahoma Aquarium, USA. Captive.

Joel Sartore / Photo Ark / Two Yosemite toad (Anaxyrus canorus) juveniles, side by side, one with mouth open, portrait, Museum of Vertebrate Zoology at U.C. Berkeley, California, USA. Captive. Endangered.

David Pattyn / Double-striped thick-knee (Burhinus bistriatus) stretching its leg, Los Llanos, Colombia.

David Pattyn / Burrowing owl (Athene cunicularia) standing on one leg on wooden post, Llanos, Colombia.

Neil Aldridge / Cheetah (Acinonyx jubatus) male coalition sniffing and scent marking fallen branch and tree, in early morning light. One animal defecates on the branch. Okavango Delta, Botswana.

Neil Aldridge / Cheetah (Acinonyx jubatus) males using a fallen tree as a lookout in early morning light. One male leaves the frame and the other sniffs the tree for a scent marking. Okavango Delta, Botswana.

David Tipling / Eurasian otter (Lutra lutra) mother and cubs resting on seaweed covered rock beside water, with one cub placing paws on mother's back, Shetland, Scotland, UK. November.

David Tipling / Two Tree sparrow (Passer montanus) males perched on roof, one with nesting material in beak, Bempton RSPB visitor centre, Yorkshire, UK. April.

Franco Banfi / Herd of European bison (Bison bonasus) resting with one standing and looking around, in field beside forest, Bialowieza Forest UNESCO World Heritage Site, Poland.

Brian Bevan / Close up of Red-eyed tree frog (Agalychnis callidryas) tadpoles developing in spawn with one egg remaining undeveloped. Captive.

Brian Bevan / Peregrine falcon (Falco peregrinus) chicks looking out of nest entrance in window, with one bobbing its head to judge distance, Bedfordshire, UK.

Staffan Widstrand / Black stork (Ciconia nigra) pair, one preening the other during courtship, Kiskunsagi National Park, Pusztaszer, Hungary. May.

Staffan Widstrand / Black stork (Ciconia nigra) pair standing in shallow water, one preening the other during courtship, Kiskunsagi National Park, Pusztaszer, Hungary. May.

Neil Aldridge / White-fronted bee-eater (Merops bullockoides) pair perching on branch, one takes off and leaves frame, before entering frame and landing on the branch again with a bee in it's beak, which it wipes on...

Neil Aldridge / White-fronted bee-eater (Merops bullockoides) pair perching on a branch, one takes flight and leaves frame, Luvuvhu River, Makuleke, Great Limpopo Transfrontier Park, South Africa.

Neil Aldridge / Common flat lizard (Platysaurus intermedius) female and juveniles basking on rock, with one juvenile entering the frame to sit next to the female, Mapungubwe National Park, Greater Mapungubwe Transfro...

Vishal Jadhav / Malabar pied hornbill (Anthracoceros coronatus) male regurgitating figs, feeding them to the female inside the nest hole and dropping one whilst he perches at entrance, Chiplun, Maharashtra, India, Ap...

Doug Gimesy / Bottlenose dolphins (Tursiops truncatus) riding bow wave of ship as one breaches and looks towards sky, Milford Sound, Fiordland, New Zealand, January.

Jouan & Rius / Greater flamingo (Phoenicopterus roseus) flock resting on one leg in still water with reflections, Camargue, France.

Jouan & Rius / Greater flamingo (Phoenicopterus roseus) flock sleeping whilst standing one one leg in reflective water, Camargue, France, January.

Jouan & Rius / Greater flamingo (Phoenicopterus roseus) flock standing in lake as others fly overhead and one bird flaps its wings, Camargue, France, January.

Jouan & Rius / Two Common guillemots (Uria aalge) perched on sea cliff, one with bridled plumage, Isle of Lunga, Treshnish Isles, Inner Hebrides, Scotland, UK, May.

Tom Vierus / Fiji goshawk (Accipiter rufitorques) perched with one foot raised. The animal is calling. This species is endemic to Fiji. Suva, Viti Levu, Fiji.

George Sanker / Osprey (Pandion haliaetus) pair at nest site, one returning to nest with fish prey, Everglades National Park, Florida, USA. March.

Joel Sartore / Photo Ark / Ranges stone gecko (Diplodactylus furcosus) male with hatchling, aged one month, portrait, private collection, Texas. Captive, occurs in Australia.

Joel Sartore / Photo Ark / Ranges stone gecko (Diplodactylus furcosus) male with hatchling, aged one month, portrait, private collection, Texas. Captive, occurs in Australia.

Suzi Eszterhas / Veterinarian examining infant Bornean orangutan (Pongo pygmaeus) aged one year, Borneo, Indonesia, February, 2012. Endangered.

Suzi Eszterhas / Eastern grey kangaroo (Macropus giganteus) joey, aged one year, suckling from teat within mothers pouch, Brisbane, Australia. Captive.

Doug Gimesy / Spectacled flying foxes (Pteropus conspicullatus) hanging upside down in tree, as one flaps its wings to cool itself, Queensland, Australia. Endangered.

Manuel Gracia / Whiskered tern (Chlidonias hybrida) pair on nest, one incubates clutch of eggs as the other organises the nest and then flies off, leaving frame, Donana National Park, Sevilla, Spain.

Manuel Gracia / Two Whiskered tern (Chlidonias hybrida) fledglings on and beside nest, as one exercises it's wings in preparation for flight, Donana National Park, Sevilla, Spain.

Manuel Gracia / Whiskered tern (Chlidonias hybrida) parent enters frame and delivers frog to nest of three chicks before leaving frame, one of the chicks struggles to eat it, leading its sibling to try and take the f...

Manuel Gracia / Whiskered tern (Chlidonias hybrida) rearranges nest before flying off and leaving frame as one chick defecates off the edge of the nest whilst another chick rests on the nest, Donana National Park, Se...

Manuel Gracia / Whiskered tern (Chlidonias hybrida) parent enters frame and delivers frog to nest of three chicks before leaving frame, two of the chicks fight over it before one swallows it, Donana National Park Sav...

Manuel Gracia / Whiskered tern (Chlidonias hybrida) parent enters frame and delivers fish to nest of two chicks, feeding it to one chick, landing on the nest before taking off and leaving frame, Donana National Park,...

Manuel Gracia / Whiskered tern (Chlidonias hybrida) parent enters frame, delivers fish to nest of two chicks, feeds one and flies off, leaving frame, Donana National Park, Sevilla, Spain.

Espen Bergersen / Two Northern gannets (Morus bassanus) perched on rock, one spreading its wings, Nordland, Norway. August.

Espen Bergersen / Two Great cormorants (Phalacrocorax carbo sinensis) standing in shallow water, one shaking its feathers dry, Hungary. February.

Bernard Castelein / Hamerkop (Scopus umbretta) standing on riverbank holding a feather in beak, scratching and preening, Allahein river, The Gambia.

Sergey Gorshkov / Two Sika deer (Cervus nippon) females standing on frozen pool in forest, with one female standing on on the tips of her back hooves, Land of the Leopard National Park, Russian Far East. Taken with rem...

Sergey Gorshkov / Sika deer (Cervus nippon) herd walking past fallen tree in forest as one looks around, Land of the Leopard National Park, Russian Far East. Taken with remote camera. June.

Staffan Widstrand / Two Nanday parakeets (Aratinga nenday) perched on branch, one preening the other, Pantanal wetlands, Mato Grosso do Sul, Brazil.

Staffan Widstrand / Two Nanday parakeets (Aratinga nenday) perched on branch, one preening the other, Pantanal wetlands, Mato Grosso do Sul, Brazil.

Staffan Widstrand / Two Red and green macaws (Ara chloropterus) perched on branch, one preening the other, Burraco das Araras, Pantanal wetlands, Mato Grosso do Sul, Brazil.

Robin Chittenden / Two Wood pigeons (Columba palumbus), one perched on wooden bench, the other taking flight, Norwich, UK. July.

Henley Spiers / Giant damselfish (Microspathodon dorsalis) male, protecting its nest during breeding season from attack by hungry Cortez rainbow wrasse (Thalassoma lucasanum) initial phase and one in terminal phase,...

Ugo Mellone / Iberian ibex (Capra pyrenaica), female, feeding while kid, aged between one and two months, pesters. Sierra Nevada National Park, Andalusia, Spain. May.

Ugo Mellone / Iberian ibex (Capra pyrenaica) twins, aged between one and two months, suckling from mother. Sierra Nevada National Park, Andalusia, Spain. May.

Ugo Mellone / Iberian ibex (Capra pyrenaica) kids, aged between one and two months, playfighting. Sierra Nevada National Park, Andalusia, Spain. May.

Ugo Mellone / Iberian ibex (Capra pyrenaica) kids, aged between one and two months, climbing over rocks. Sierra Nevada National Park, Andalusia, Spain. May.

Ugo Mellone / Iberian ibex (Capra pyrenaica), adult female, grazing with kid, aged between one and two months. Sierra Nevada National Park, Andalusia, Spain. May.

Ugo Mellone / Iberian ibex (Capra pyrenaica), two adult females with kid aged between one and two months, climbing over rocks. Sierra Nevada National Park, Andalusia, Spain. May.

Ugo Mellone / Iberian ibex (Capra pyrenaica), alert female with kid aged between one and two months. Sierra Nevada National Park, Andalusia, Spain. May.

Robin Chittenden / Two Avocets (Recurvirostra avosetta) on water, one displaying aggressive behaviour towards the other, Titchwell, Norfolk, UK. August.

David Tipling / Blue tit (Cyanistes caeruleus) pair at nest box in garden, one perched at entrance with caterpillar in beak, Norfolk, UK. May.

Franco Banfi / Three California sea lions (Zalophus californianus) in an underwater cave, one playing with a seastar, Espiritu Santo Island, Baja California, Mexico, Sea of Cortez.

Joel Sartore / Photo Ark / Spoon-billed sandpiper (Calidris pygmaea) with prey in beak, portrait, Wildfowl and Wetlands Trust Slimbridge, UK. This individual is one of the remaining birds from a captive rearing project undertak...

Joel Sartore / Photo Ark / Spoon-billed sandpiper (Calidris pygmaea) with prey in beak, portrait, Wildfowl and Wetlands Trust Slimbridge, UK. This individual is one of the remaining birds from a captive rearing project undertak...

Joel Sartore / Photo Ark / Spoon-billed sandpiper (Calidris pygmaea) catching insect prey, portrait, Wildfowl and Wetlands Trust Slimbridge, UK. This individual is one of the remaining birds from a captive rearing project under...

Joel Sartore / Photo Ark / Spoon-billed sandpiper (Calidris pygmaea) feeding, portrait, Wildfowl and Wetlands Trust Slimbridge, UK. This individual is one of the remaining birds from a captive rearing project undertaken as part...

Joel Sartore / Photo Ark / Spoon-billed sandpiper (Calidris pygmaea) with prey in beak, portrait, Wildfowl and Wetlands Trust Slimbridge, UK. This individual is one of the remaining birds from a captive rearing project undertak...

Tony Heald / Lesserr flamingo (Phoeniconaias minor) flock resting at sunset. Amboseli National Park, Kenya. July.

David Pattyn / Two Great crested grebe (Podiceps cristatus) chicks on water, with one stretching wings, in early morning light, Valkenhorst nature reserve, Valkenswaard, The Netherlands. June.

David Pattyn / Great crested grebe (Podiceps cristatus) on water with two chicks, carrying one on its back, Valkenhorst nature reserve, Valkenswaard, The Netherlands. June.

David Pattyn / Great crested grebe (Podiceps cristatus) on water with two chicks, carrying one on its back, Valkenhorst nature reserve, Valkenswaard, The Netherlands. June.

Harry Collins / Peregrine falcon (Falco peregrinus) shaking feathers whilst perched on tree branch. It lifts up one foot so that it stands on one leg, New Jersey, USA. March.

Lewis Jefferies / Common black hawk (Buteogallus anthracinus) perched on one leg, on branch in forest whilst surveying the forest floor, Corcovado National Park, Costa Rica.

Roger Powell / Pair of Bearded vultures (Gypaetus barbatus), one full adult and one sub-adult, engaging in courtship display in flight. Lamiana, Aragon, Spanish Pyrenees, Spain. April.

Roger Powell / Pair of Bearded vultures (Gypaetus barbatus), one full adult and one tagged sub-adult, engaging in courtship display in flight. Lamiana, Aragon, Spanish Pyrenees, Spain. April.

Roger Powell / Pair of Bearded vultures (Gypaetus barbatus), one full adult and one tagged sub-adult, engaging in courtship display in flight. Lamiana, Aragon, Spanish Pyrenees, Spain. April.

Roger Powell / Small flock of Griffon vultures (Gyps fulvus) circling and soaring on thermals, with one Bearded vulture (Gypaetus barbatus) top right. Lamiana, Aragon, Spanish Pyrenees, Spain. May.

Franco Banfi / Pod of Sperm whales (Physeter macrocephalus) at sea surface, with one spyhopping. Dominica. Caribbean Sea, Atlantic Ocean.

Tui De Roy / Royal Tern (Thalasseus maximus) preying on newly hatched Olive ridley turtle (Lepidochelys olivacea), holding one in beak. Playa Escobilla Sanctuary, Oaxaca, Mexico. Pacific Ocean.

Tui De Roy / Royal Tern (Thalasseus maximus) preying on newly hatched Olive ridley turtle (Lepidochelys olivacea), holding one in beak. Playa Escobilla Sanctuary, Oaxaca, Mexico. Pacific Ocean.

Tui De Roy / Royal Tern (Thalasseus maximus) preying on newly hatched Olive ridley turtle (Lepidochelys olivacea), holding one in beak. Playa Escobilla Sanctuary, Oaxaca, Mexico. Pacific Ocean.

Tui De Roy / Royal Tern (Thalasseus maximus) preying on newly hatched Olive ridley turtle (Lepidochelys olivacea), holding one in beak. Playa Escobilla Sanctuary, Oaxaca, Mexico.

Tui De Roy / Royal Tern (Thalasseus maximus) preying on newly hatched Olive ridley turtle (Lepidochelys olivacea), holding one in beak, being chased by two Magnificent frigatebird (Fregata magnificens). Playa Es...

Tui De Roy / Three female Olive ridley turtles (Lepidochelys olivacea) coming ashore to nest at night while one leaves during massive arribada. Playa Escobilla Sanctuary, Oaxaca, Mexico. Pacific Ocean.

Tui De Roy / American flamingo (Phoenicopterus ruber) with chick, standing on one leg. Rabida Island, Galapagos Islands, Ecuador.

Tui De Roy / Pair of American flamingos (Phoenicopterus ruber) standing on one leg, with chick. Rabida Island, Galapagos Islands, Ecuador.

Tui De Roy / Pair of Swallow-tailed gulls (Creagrus furcatus) at nest, one incubating. Genovesa Island, Galapagos Islands, Ecuador.

Tui De Roy / Pair of Swallow-tailed gulls (Creagrus furcatus) at nest, one incubating, other preening. Genovesa Island, Galapagos Islands, Ecuador.

Tui De Roy / Pair of Swallow-tailed gulls (Creagrus furcatus) at nest, one incubating. Genovesa Island, Galapagos Islands, Ecuador.

Tui De Roy / Pair of Swallow-tailed gulls (Creagrus furcatus) at nest, one incubating, one calling. Genovesa Island, Galapagos Islands, Ecuador.