Donald M. Jones / Mountain Bluebird (Sialia currucoides) male in nest cavity, Troy, Montana

Pete Oxford / Huaorani Indian and his child outside their forest dwelling. Bameno Community, Yasuni National Park, Ecuador, May 2007. Model release B#6.

Jim Brandenburg / Black-footed Ferret (Mustela nigripes) smelling ground, Wyoming

Steve Gettle / Barn Swallow (Hirundo Rustica) feeding chicks in nest, Michigan

Steve Gettle / Barn Swallow (Hirundo Rustica) feeding, Michigan

Alex Hyde / Ground Dwelling tree frog (Gephyromantis / Mantidactylus webbi) camouflaged against moss. Masoala Peninsula National Park, north east Madagascar. IUCN endangered species

Tui De Roy / Great Frigatebird (Fregata minor) female guarding chick, Galapagos Islands, Ecuador

Steve Gettle / Sandhill Crane (Grus canadensis) incubating unhatched egg on nest with already born chick, Kensington Metropark, Michigan

Konrad Wothe / Fennec Fox (Vulpes zerda) looking out of den, Libya

Donald M. Jones / Common Starling (Sturnus vulgaris) chick peeking out of nest cavity, western Montana

Mark Moffett / Amazon Ant (Polyergus sp) group returning to their home nest at the conclusion of a slave raid, grey slave ant carries one of their pupa, near Lake Tahoe, California

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) with chick, Saunders Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) with chick, Saunders Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) with chick on pedestal nest, Saunders Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) nesting colony, Steeple Jason Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) on pedestal nest, Steeple Jason Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) on nest, Keppel Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) on pedestal nest, Keppel Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) on pedestal nest, Keppel Island, Falkland Islands

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) on pedestal nest, Keppel Island, Falkland Islands

Konrad Wothe / Satin Bowerbird (Ptilonorhynchus violaceus) male arranging blue ornaments to impress female in bower, Victoria, Australia

Jouan & Rius / Endemic frog (Mantidactylus liber) on leaf in rainforest, Andasibe Mantadia NP, Madagascar

Jouan & Rius / Endemic frog (Mantidactylus liber) at night in rainforest, Andasibe Mantadia NP, Madagascar

Tui De Roy / Campbell Albatross (Thalassarche impavida) parent guarding chick, North Cape, Campbell Island, sub-Antarctica New Zealand

Luciano Candisani / Black-browed Albatross (Thalassarche melanophrys) chick begging parent for food, Saunders Island, Falkland Islands

Heidi & Hans-Juergen Koch / Honey Bee (Apis mellifera) natural beehive, built in wooden hut in the garden of the Bee Station at the Bavarian Julius-Maximilians-University of Wurzburg, Germany

Tom Vezo / Acorn Woodpecker (Melanerpes formicivorus) female bringing food to nest cavity, Madera Canyon, Arizona

Yva Momatiuk & John Eastcott / Black-browed Albatross (Thalassarche melanophrys) chick, New Island, Falkland Islands

Yva Momatiuk & John Eastcott / Black-browed Albatross (Thalassarche melanophrys) chick, New Island, Falkland Islands

Birgitte Wilms / Tube-dwelling Anemone, detail of tentacles, Indonesia

Konrad Wothe / Resplendent Quetzal (Pharomachrus mocinno) male looking out of nest, Costa Rica

Chris Newbert / Black-rayed Shrimpgoby (Stonogobiops nematodes) with Shrimp guarding burrow, 80 feet deep, Papua New Guinea

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

Mark Raycroft / Cairn Terrier (Canis familiaris) on deck

Michael Quinton / Great Gray Owl (Strix nebulosa) parent protecting eggs in nest, North America

Michael Quinton / Great Gray Owl (Strix nebulosa) incubating eggs on nest, North America

Pete Oxford / Ancient dwelling remains on Skeleton coast, Namibia

Michael Durham / Brown Rat (Rattus norvegicus) raiding urban garbage, common pest species native to Europe, introduced worldwide

Konrad Wothe / Boreal Owl (Aegolius funereus) in nest cavity, Sweden

Michio Hoshino / Snowy Owl (Nyctea scandiaca) parent and chicks at tundra nest, Alaska

Fred Bavendam / Pink Anemonefish (Amphiprion perideraion) nestled among the tentacles of its Sea Anemone host, Coral Sea, Queensland, Australia

Mark Moffett / Weaver Ant (Oecophylla longinoda) group grab an adjacent leaf and stem with mandibles and toes and pull, gradually binding them together to make a nest, Malaysia

Mark Moffett / Weaver Ant (Oecophylla longinoda) group grab an adjacent leaf and stem with mandibles and toes and pull, gradually binding them together to make a nest, Malaysia

Mark Moffett / Leafcutter Ant (Atta cephalotes) workers carrying leaves to nest, French Guiana

Mark Moffett / Leafcutter Ant (Atta cephalotes) workers carrying leaves to nest, French Guiana

Flip de Nooyer / Eurasian Kestrel (Falco tinnunculus) group of five juveniles in nesting box, Europe

Flip de Nooyer / Common Vole (Microtus arvalis) adult peering from burrow, Europe

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

Jim Brandenburg / Bald Eagle (Haliaeetus leucocephalus) bringing fish to mate in nest, Northwoods, Minnesota

Michael & Patricia Fogden / Common Egg-eating Snake (Dasypeltis scabra) swallowing egg from another animal's nest, savannah, South Africa

Flip Nicklin / Sandbar Shark (Carcharhinus plumbeus) underwater portrait, bottom-dwelling coastal species, worldwide distribution

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

Fred Bavendam / Pacific Giant Octopus (Enteroctopus dofleini) female guarding her eggs, Quadra Island, British Columbia, Canada

Jim Brandenburg / Black-tailed Prairie Dog (Cynomys ludovicianus) trio at burrow entrance, South Dakota

Michael Quinton / Red Squirrel (Tamiasciurus hudsonicus) four young at entrance to their nest in a tree cavity, Alaska

Michael & Patricia Fogden / Emerald Toucanet (Aulacorhynchus prasinus) eating Passion Fower (Passiflora sp) fruit at nest cavity, cloud forest, Costa Rica

Tom Vezo / Piping Plover (Charadrius melodus) sitting on eggs in nest on ground, Long Island, New York

Gerry Ellis / Honey Bee (Apis mellifera) group feeding on honeycomb, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother returning to her 35 day old babies in nest to nurse them, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) curious 40 day old babies peer out from nest in tree trunk, Rocky Mountains, North America

Tom Vezo / Ferruginous Pygmy Owl (Glaucidium brasilianum) adult peering out from nest hole in Saguaro (Cereus gigantea) cactus, Altar Valley, Arizona

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing her 15 day old babies in nest, Rocky Mountains, North America

Konrad Wothe / Barn Swallow (Hirundo rustica) chicks lined up in nest with their mouths open waiting for food, Germany

Yva Momatiuk & John Eastcott / Gila Woodpecker (Melanerpes uropygialis) nesting in Saguaro (Carnegiea gigantea) in desert, spring, Sonoran Desert National Monument, Arizona

Konrad Wothe / Boreal Owl (Aegolius funereus) in nest cavity, Sweden

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

Claus Meyer / Yellow Armadillo (Euphractus sexcinctus) peeking out of burrow, Caatinga ecosystem, Brazil

Gerry Ellis / Magnificent Hummingbird (Eugenes fulgens) nest with three eggs, Costa Rica

Gerry Ellis / Gentoo Penguin (Pygoscelis papua) parent and chicks begging for food on nest, South Georgia Island

Konrad Wothe / Blue Tit (Cyanistes caeruleus) parent delivering caterpillar to chicks in nest, Europe

Chris Newbert / Freckle Face Blenny (Istiblennius chrysospilos) in burrow, five feet deep, Solomon Islands

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

Chris Newbert / Hermit Crab (Paguritta gracilipes) in Hump Coral (Porites sp) 30 feet deep, Solomon Islands

Flip de Nooyer / Common Eider (Somateria mollissima) adult female at down nest with eggs, Europe

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing babies in nest, Rocky Mountains, North America

Sumio Harada / American Robin (Turdus migratorius) newly-hatched day old chicks begging in nest with unhatched blue egg, Glacier National Park, Montana

Gerry Ellis / Great Bowerbird (Chlamydera nuchalis) male in courting bower, Katherine Gorge National Park, Australia

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

Matthias Breiter / Great Bowerbird (Chlamydera nuchalis) male displaying in front of female in lek, Australia

Gerry Ellis / American Beaver (Castor canadensis) dam, Silver Horn Creek, Lake Silver Horn, Wood River, Wood-Tikchik State Park, Alaska

Konrad Wothe / Kentish Plover (Charadrius alexandrinus) male at nest, Europe

Larry Minden / Desert Tortoise (Gopherus agassizii) emerging from burrow beneath Mohave Desertrue (Thamnosma montana), Mojave Desert, California

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

Mark Moffett / Weaver Ant (Oecophylla longinoda) group building nest by pulling on leaves and forming chains, Africa

Mark Moffett / Herdsman Ant (Dolichoderus cuspidatus) queen surrounded by guards, marches along as the ants shift the site of their nest, Malaysia

Mark Moffett / Fire Ant (Solenopsis geminata) nest showing large queen, workers and pupa, Florida

Mark Moffett / Weaver Ant (Oecophylla longinoda) group repairing leaf nest, Papua New Guinea

Jim Brandenburg / Western Grebe (Aechmophorus occidentalis) nest with egg floating in prairie pothole, Aberdeen, South Dakota

Michael Quinton / Red-necked Grebe (Podiceps grisegena) parent on nest with eggs in boreal pond, Alaska

Michael Quinton / Bald Eagle (Haliaeetus leucocephalus) returning to nest with food for chicks, Alaska

Michael Quinton / Northern Hawk Owl (Surnia ulula) at nest with chicks, Alaska

Tui De Roy / Blue-footed Booby (Sula nebouxii) male incubating eggs with webbed feet, Seymour Island, Galapagos Islands, Ecuador

Jim Brandenburg / Black-tailed Prairie Dog (Cynomys ludovicianus) town with animals near burrows, South Dakota

Jim Brandenburg / Black-tailed Prairie Dog (Cynomys ludovicianus) barking while standing atop burrow, South Dakota