Gary Bell/ Oceanwide / Australian Giant Cuttlefish (Sepia apama) group gathered for mating, Whyalla, South Australia, Australia

Marie Read / Baltimore oriole (Icterus galbula) male perched in pear (Pyrus sp.) blossom, eastern redbud in background, New York, USA. May.

Luciano Candisani / Green Anaconda (Eunectes murinus) female constricting male after copulation, after which she will consume him, Brazil

Steve Gettle / Great Egret (Ardea alba) in courtship display, North America

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) group migrating upstream, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Ingo Arndt / Sockeye Salmon (Oncorhynchus nerka) group swimming upstream during spawning run, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Donald M. Jones / Nashville Warbler (Oreothlypis ruficapilla) male calling in spring, western Montana

Winfried Wisniewski / Ruff (Philomachus pugnax) males displaying in rain at lek, Norway

Winfried Wisniewski / Ruff (Philomachus pugnax) male displaying at lek, Varanger Peninsula, Norway

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) migrating upstream, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Tui De Roy / Takahe (Porphyrio hochstetteri) family in large breeding pen, Burwood Breeding Center, New Zealand

Sebastian Kennerknecht / Atlantic Puffin (Fratercula arctica) at nest burrow, Skomer Island National Nature Reserve, Skomer Island, Pembrokeshire, Wales, United Kingdom

Roland Seitre / Hispaniolan amazon (Amazona ventralis) captive at breeding centre, from Hispaniola. Vulnerable species.

Glenn Bartley / Eared Grebe (Podiceps nigricollis), British Columbia, Canada

Walter Soestbergen / Eared Grebe (Podiceps nigricollis) male in breeding plumage, Utrecht, Netherlands

Glenn Bartley / Willow Ptarmigan (Lagopus lagopus) male, Manitoba, Canada

Matthias Breiter / Red-sided Garter Snake (Thamnophis sirtalis parietalis) group mating after hibernation, Narcisse, Manitoba, Canada

Cyril Ruoso / Common Frog (Rana temporaria) group in breeding pond at around 2000 meters, Alps, France

Cyril Ruoso / Common Frog (Rana temporaria) group on ice covering parts of breeding pond at around 2000 meters, Alps, France

Cyril Ruoso / Giant Panda (Ailuropoda melanoleuca) two cubs playing, Chengdu Panda Breeding Research Center, China

Cyril Ruoso / Giant Panda (Ailuropoda melanoleuca) female with year old cubs playing, Chengdu Panda Breeding Research Center, China

Cyril Ruoso / Giant Panda (Ailuropoda melanoleuca) female and year old cub playing, Chengdu Panda Breeding Research Center, China

Cyril Ruoso / Giant Panda (Ailuropoda melanoleuca) year old cub in a tree, Chengdu Panda Breeding and Research Center, Sichuan, China

Donald M. Jones / Common Loon (Gavia immer) stretching wings, Troy, Montana

Steve Gettle / Wood Duck (Aix sponsa) male swimming, Lapeer State Game Area, Michigan

Steve Gettle / Ring-necked Duck (Aythya collaris) male flying, Island Lake Recreation Area, Michigan

Steve Gettle / Wood Duck (Aix sponsa) male in breeding plumage, Lapeer State Game Area, Michigan

Steve Gettle / Wood Duck (Aix sponsa) male in breeding plumage, Lapeer State Game Area, Michigan

Steve Gettle / Wood Duck (Aix sponsa) male flying, Lapeer State Game Area, Michigan

Richard Du Toit / Long-tailed Widow (Euplectes progne) male in breeding plumage, South Africa

Hiroya Minakuchi / Nudibranch (Hypselodoris bullockii) pair mating, Borneo, Malaysia

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) group swimming in fast current during spawning run, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) group swimming upstream between forested banks during spawning run, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) group swimming upstream between forested banks during spawning run, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Yva Momatiuk & John Eastcott / Sockeye Salmon (Oncorhynchus nerka) group swimming close to surface during spawning run, Adams River, Roderick Haig-Brown Provincial Park, British Columbia, Canada

Vincent Grafhorst / African Lion (Panthera leo) pair mating, Khutse Game Reserve, Botswana

Donald M. Jones / Eared Grebe (Podiceps nigricollis) mother carrying newborn chick, central Montana

Sebastian Kennerknecht / Common Goldeneye (Bucephala clangula) male in breeding plumage on pond, Santa Cruz, Monterey Bay, California

Sebastian Kennerknecht / Ring-necked Duck (Aythya collaris) drake in breeding plumage calling, Santa Cruz, Monterey Bay, California

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) 37 day old cub, Ying Ying, in incubator, Wolong Nature Reserve, endangered, China

Jim Brandenburg / Common Loon (Gavia immer) swimming, Minnesota

Vincent Grafhorst / African Lion (Panthera leo) pair copulating, Moremi Game Reserve, Okavango Delta, Botswana

Vincent Grafhorst / African Lion (Panthera leo) pair copulating, Moremi Game Reserve, Okavango Delta, Botswana

Yva Momatiuk & John Eastcott / Southern Elephant Seal (Mirounga leonina) bull roaring at intruder on beach during breeding season, Gold Harbour, South Georgia Island

Thomas Marent / Golden Poison Dart Frog (Phyllobates terribilis) pair mating, Cauca, Colombia

Scott Leslie / American Goldfinch (Carduelis tristis) male in breeding plumage, Nova Scotia, Canada

Mitsuaki Iwago / Giant Panda (Ailuropoda melanoleuca), three captive bred cubs, China

Mitsuaki Iwago / Giant Panda (Ailuropoda melanoleuca) portrait, captive bred, Wolong, Sichuan, China

Mitsuaki Iwago / Giant Panda (Ailuropoda melanoleuca), captive bred cub, China

Tom Vezo / Western Tanager (Piranga ludoviciana) male, Rio Grande Valley, Texas

Tom Vezo / Cape May Warbler (Setophaga tigrina) male, Rio Grande Valley, Texas

Thomas Mangelsen / King Penguin (Aptenodytes patagonicus) group of downy chicks, Fortuna Bay, South Georgia

Mitsuaki Iwago / African Lion (Panthera leo) mating pair quarreling, Serengeti National Park, Tanzania

Yva Momatiuk & John Eastcott / California Condor (Gymnogyps californianus) adult with wingspan of 9 feet flying, critically endangered, bred in captivity, later released, and wearing radio transmitter, near Zion National Park, Utah

Christian Ziegler / Army Ant (Eciton hamatum) colony forming a bridge by climbing over each other, some are carrying food back to nest, Barro Colorado Island, Panama

ZSSD / Panamanian Golden Frog (Atelopus zeteki) pair in amplexus, native to Panama

Mitsuaki Iwago / African Lion (Panthera leo) couple mating, Serengeti National Park, Tanzania

Tui De Roy / Marine Iguana (Amblyrhynchus cristatus) breeding male basking with Sally Lightfoot Crab (Grapsus grapsus) scavenging dead skin, Hood Island, Galapagos Islands, Ecuador

Flip de Nooyer / Black-browed Albatross (Thalassarche melanophrys) chicks on tower nests, South Georgia Island

Tui De Roy / Salvin's Albatross (Thalassarche salvini) returning en masse to crowded nesting colony at sunset, Proclamation Island, Bounty Islands, New Zealand

Mitsuaki Iwago / African Lion (Panthera leo) couple fighting during mating, Serengeti National Park, Tanzania

Sumio Harada / Black-footed Ferret (Mustela nigripes) emerging from burrow in ground, recently released from captive breeding program onto the Fort Belknap Indian Reservation, Montana

Sumio Harada / Black-footed Ferret (Mustela nigripes) emerging from burrow in ground, recently released from captive breeding program onto the Fort Belknap Indian Reservation, Montana

Sumio Harada / Black-footed Ferret (Mustela nigripes) emerging from burrow in ground, recently released from captive breeding program onto the Fort Belknap Indian Reservation, Montana

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) Gongzhu is successfully re-introduced to one of her nine week old twin cubs which she initially rejected, China Conservation and Research Center for the Giant Pand...

Yva Momatiuk & John Eastcott / Atlantic Puffin (Fratercula arctica) pair in their bright breeding colors, during summer breeding season on coastal cliffs, Newfoundland, Canada

Yva Momatiuk & John Eastcott / Atlantic Puffin (Fratercula arctica) adults congregate in colony on coastal cliff during summer breeding season, Newfoundland, Canada

Yva Momatiuk & John Eastcott / Black-bellied Plover (Pluvialis squatarola) non-breeding bird resting on one leg on shore, spring, Gulf of Mexico, Padre Island National Seashore, Texas

Pete Oxford / Emperor Penguin (Aptenodytes forsteri) pair, Flutter EP Rookery, Cape Darnley, Australian Antarctic Territory, Antarctica

Gordon Court / Adelie Penguin (Pygoscelis adeliae) gives a warning call when under threat, Cape Bird, Ross Island, Antarctica

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) mother and two week old infant, Wolong Nature Reserve, China

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) mother and her cub at the China Conservation and Research Center for the Giant Panda, Wolong Nature Reserve, China

Michael & Patricia Fogden / Golden Toad (Bufo periglenes) male, breeding aggregation, extinct, Monteverde Cloud Forest Reserve, Costa Rica

Chris Newbert / Right-handed Hermit Crab (Paguritta sp) colony in Hump Coral (Porites sp), Solomon Islands

Gerry Ellis / Greater Flamingo (Phoenicopterus ruber) nesting colony with mud nests, Inagua National Park, Bahamas

Mark Moffett / Fire Ant (Solenopsis geminata) colony with queen ant, workers and pupae, Florida

Tui De Roy / Atlantic Puffin (Fratercula arctica) at entrance to nesting burrow during breeding season, Skomer Island, Wales

Tui De Roy / Campbell Albatross (Thalassarche impavida) coming in to land, Bull Rock Cape Colony, Campbell Island, New Zealand

Mark Moffett / True Weevil (Eupholus sp) pair mating, Hala, Papua New Guinea

Tim Fitzharris / American Avocet (Recurvirostra americana) wading through shallow water, North America

Tim Fitzharris / Roseate Spoonbill (Platalea ajaja) adult in breeding plumage, North America

Tim Fitzharris / Roseate Spoonbill (Platalea ajaja) adult in breeding plumage standing in golden-colored water, North America

Fred Bavendam / Stony Coral (Acropora sp) colony releasing egg-sperm bundles during the mass coral spawning each March at Ningaloo Reef, Western Australia

Tui De Roy / King Penguin (Aptenodytes patagonicus) group swimming underwater offshore from breeding colony, Macquarie Island, sub-Antarctica Australia

Tui De Roy / Royal Penguin (Eudyptes schlegeli) group walking to colony past Macquarie Island Cabbage (Stilbocarpa polaris) both endemic to Macquarie Island, Australia

Tui De Roy / Great Spotted Kiwi (Apteryx haastii) male in rainforest habitat, Kiwi House, Otorohanga Breeding Facility, New Zealand

Tui De Roy / Blue-footed Booby (Sula nebouxii) pair overlooking nesting colony, Punta Vicente, Isabella Island, Galapagos Islands, Ecuador

Tui De Roy / King Penguin (Aptenodytes patagonicus) group underwater, offshore from breeding colony, Macquarie Island, sub-Antarctica Australia

Tui De Roy / Great Spotted Kiwi (Apteryx haastii) male in rainforest habitat, Kiwi House, Otorohanga Breeding Facility, New Zealand

Tui De Roy / Great Spotted Kiwi (Apteryx haastii) breeding pair showing size difference, female 30% larger, Kiwi House, Otorohanga Breeding Facility, New Zealand

Tui De Roy / Emperor Penguin (Aptenodytes forsteri) group tobogganing across vast distance of fast ice to nesting rookery, Kloa Point, Edward VIII Gulf, Antarctica

Tui De Roy / King Penguin (Aptenodytes patagonicus) group swimming underwater offshore from breeding colony, Macquarie Island, sub-Antarctica Australia

Tui De Roy / King Penguin (Aptenodytes patagonicus) group swimming underwater offshore from breeding colony, Macquarie Island, sub-Antarctica Australia

Mark Jones / Sulawesi Red-knobbed Hornbill (Aceros cassidix) breeding male in a fruiting Fig tree (Ficus forsteni) 32 meters above the ground in rainforest canopy, Tangkoko-Dua Saudara Nature Reserve, Sulawesi, In...

Mark Jones / Sulawesi Red-knobbed Hornbill (Aceros cassidix) breeding male in fruiting Fig (Ficus forsteni), Tangkoko-Dua Saudara Nature Reserve, Sulawesi, Indonesia

Michael Quinton / Common Loon (Gavia immer) parent on nest with one day old chick in the summer, Wyoming