Tui De Roy / Blue-footed Booby (Sula nebouxii) family on nest site, Punta Suarez, Hood Island, Galapagos Islands, Ecuador

Tui De Roy / Red-footed Booby (Sula sula) couple courting in Croton shrub, Wenman Island, Galapagos Islands, Ecuador

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

Tui De Roy / Brown Pelican (Pelecanus occidentalis) three chicks begging for food from freshly returned parent, Academy Bay, Santa Cruz Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Land Iguana (Conolophus subcristatus) female searching for descent route into 1, 000 meter active caldera to nest, Fernandina Island, Galapagos Islands, Ecuador

Mitsuaki Iwago / Loggerhead Sea Turtle (Caretta caretta) female laying eggs in nest in beach sand, Australia

Tui De Roy / Sulawesi Red-knobbed Hornbill (Aceros cassidix) male delivering figs to a female sealed inside hollow nest cavity, Tangkoko Dua Saudara Nature Reserve, Sulawesi, Indonesia

Tui De Roy / Blue-footed Booby (Sula nebouxii) courtship landing salute at nest site, Punta Vicente Roca, Isabella Island, Galapagos Islands, Ecuador

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 / Brown Pelican (Pelecanus occidentalis) feeding chicks by regurgitation in Mangrove (Avicennia sp) nest, Turtle Bay, Santa Cruz Island, Galapagos Islands, Ecuador

Tui De Roy / Brown Pelican (Pelecanus occidentalis) guarding chicks in Mangrove (Avicennia sp) nest, Turtle Bay, Santa Cruz Island, Galapagos Islands, Ecuador

Tui De Roy / Brown Pelican (Pelecanus occidentalis) parent guarding nestlings in salt bush thickets, Rabida Island, Galapagos Islands, Ecuador

Tui De Roy / Sulawesi Red-knobbed Hornbill (Aceros cassidix) male delivering figs to female sealed inside hollow tree, Tangkoko-Dua Saudara Reserve, Indonesia

Jim Brandenburg / Burrowing Owl (Athene cunicularia) trio peeking out of burrow in tallgrass prairie, South Dakota

Mitsuaki Iwago / Green Sea Turtle (Chelonia mydas) female digging nest in sand, Australia

Fred Bavendam / Paper Nautilus (Argonauta nodosa) is actually a pelagic Octopus, females make the parchment-like shell to carry incubating eggs, South Australia

Michael Quinton / Canada Goose (Branta canadensis) hatchlings in nest with unhatched eggs, spring, Idaho

Norbert Wu / Larvacean (Oikopleura labradorensis) house, primitive animal spins mucus web, Arctic

Michael Quinton / Common Loon (Gavia immer) chick with hatching egg in nest in the summer, Wyoming

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

Michael Quinton / Bald Eagle (Haliaeetus leucocephalus) parent feeding chick in nest, Alaska

Michael Quinton / Bald Eagle (Haliaeetus leucocephalus) calling on nest, Alaska

Mitsuaki Iwago / Galah (Eolophus roseicapilla) pair in tree nest cavity with chick, Australia

Jim Brandenburg / Burrowing Owl (Athene cunicularia) group at burrow entrance, South Dakota

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

Jim Brandenburg / Black-tailed Prairie Dog (Cynomys ludovicianus) barking while standing on its hind feet and raising the head back, a behavior known as jump-yip calling, Wind Cave National Park, South Dakota

Fred Bavendam / Giant Nudibranch (Dendronotus iris) attacking a Tube-dwelling Anemone (Pachycerianthus fimbriatus), Vancouver Island, British Columbia, Canada. Sequence 4 of 5

Michael Quinton / American Robin (Turdus migratorius) parent feeds grasshopper to chicks in nest cavity at top of a snag, summer, Idaho

Mitsuhiko Imamori / Honeypot Ant (Camponotus inflatus) repletes hanging from ceiling of larder, engorged with nectar they will regurgitate on demand to other workers, central Australia

Michael Quinton / Trumpeter Swan (Cygnus buccinator) parent and squabbling day-old cygnets, North America

Michael Quinton / Great Gray Owl (Strix nebulosa) brooding female with chick in nest cavity at top of snag in the summer, Idaho

Michael Quinton / Great Gray Owl (Strix nebulosa) parent with owlets in nest cavity at top of snag, Idaho

Tui De Roy / Adelie Penguin (Pygoscelis adeliae) nesting colony on granite outcrop, Petermann Island, Antarctica

Tui De Roy / Emperor Penguin (Aptenodytes forsteri) group, near Ekstrom Ice Shelf, Weddell Sea, Antarctica

Tui De Roy / Emperor Penguin (Aptenodytes forsteri) group, near Ekstrom Ice Shelf, Weddell Sea, Antarctica

Mitsuaki Iwago / Loggerhead Sea Turtle (Caretta caretta) hatchling emerging from underground nest on sandy beach, Australia

Mitsuaki Iwago / Honeypot Ant (Camponotus inflatus) repletes hanging from ceiling of larder, engorged with nectar they will regurgitate on demand to other workers, central Australia

Mitsuaki Iwago / Honeypot Ant (Camponotus inflatus) repletes hanging from ceiling of larder, engorged with nectar they will regurgitate on demand to other workers, central Australia

Shin Yoshino / Osprey (Pandion haliaetus) carrying branch to nesting site, Earthquake Lake, Idaho

Jim Brandenburg / Horned Lark (Eremophila alpestris) chicks in nest on prairie with Pasque Flower (Pulsatilla sp) group, Minnesota

Shin Yoshino / Ural Owl (Strix uralensis) returning to nest, Nagasaki, Japan

Jim Brandenburg / Black-tailed Prairie Dog (Cynomys ludovicianus) in burrow with American Bison (Bison bison) and Ponderosa Pines (Pinus ponderosa), Wind Cave National Park, South Dakota

Michio Hoshino / Polar Bear (Ursus maritimus) cub nuzzling mother, Churchill, Manitoba, Canada

Michio Hoshino / Snowy Owl (Nyctea scandiaca) parent landing on tundra nest with owlets, Alaska

Jim Brandenburg / Ferruginous Hawk (Buteo regalis) and chicks on prairie nest, South Dakota

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

Mark Moffett / Nasute Termite (Nasutitermes sp) nest reveals soldiers with dart-gun heads, Amazonian Peru

Flip Nicklin / Vaquita (Phocoena sinus) by-catch casualty, Baja California, Mexico

Piotr Naskrecki / Wasp (Vespidae) nest under leaf, Suriname

Murray Cooper / Cape Buffalo (Syncerus caffer) group under tree with Yellow-billed Storks (Mycteria ibis) and nesting Marabou Storks (Leptoptilos crumeniferus), Kruger National Park, South Africa

Sebastian Kennerknecht / Cassin's Auklet (Ptychoramphus aleuticus) researchers, Jennifer Aragon, Michael Johns, and Ilana Nimz, weighing chicks taken from artifical nesting burrows near research station, South Farallon Island...

Sebastian Kennerknecht / Cassin's Auklet (Ptychoramphus aleuticus) researcher, Ilana Nimz, weighing chick taken from artifical nesting burrow near research station, South Farallon Islands, Farallon Islands, Farallon National...

Sebastian Kennerknecht / Western Gull (Larus occidentalis) nesting colony near research station, South Farallon Islands, Farallon Islands, Farallon National Wildlife Refuge, California

Sebastian Kennerknecht / Western Gull (Larus occidentalis) incubating on nest with research sign stating the nesting pattern of this individual, South Farallon Islands, Farallon Islands, Farallon National Wildlife Refuge, Cal...

Sumio Harada / Great Horned Owl (Bubo virginianus) chicks in nest on power pole, Montana

Hiroya Minakuchi / Adelie Penguin (Pygoscelis adeliae) nesting colony, Weddell Sea, Antarctic Peninsula, Antarctica

Ingo Arndt / Arctic Ground Squirrel (Spermophilus parryii) hibernating in burrow, Fairbanks, Alaska

Ingo Arndt / Arctic Ground Squirrel (Spermophilus parryii) hibernating in burrow, Fairbanks, Alaska

Ingo Arndt / Garden Dormouse (Eliomys quercinus) hibernating in old blue tit nest inside hollow tree, Germany

Ingo Arndt / Common Hamster (Cricetus cricetus) hibernating underground in nest, Germany

Ingo Arndt / Woodchuck (Marmota monax) emerging from snow after hibernation in its burrow, Minnesota

Ingo Arndt / Mew Gull (Larus canus) pair on nest, Cook Inlet, Alaska

Winfried Wisniewski / Eurasian Penduline-Tit (Remiz pendulinus) male looking out of nest, Biebrza National Park, Poland

Winfried Wisniewski / Eurasian Penduline-Tit (Remiz pendulinus) male building its nest, Biebrza National Park, Poland

ZSSD / Lesser Flamingo (Phoenicopterus minor) on nest with chick, native to Africa

Scott Leslie / Snapping Turtle (Chelydra serpentina) nest cavity with eggshells, Canada

Donald M. Jones / Ruffed Grouse (Bonasa umbellus) eggs in nest at base of tree, Troy, Montana

Donald M. Jones / Ruffed Grouse (Bonasa umbellus) eggs in nest at base of tree, Troy, Montana

Donald M. Jones / Pileated Woodpecker (Dryocopus pileatus) mother with chicks in nest cavity, Troy, Montana

Donald M. Jones / Pileated Woodpecker (Dryocopus pileatus) mother feeding chick in nest cavity, Troy, Montana

Donald M. Jones / Pileated Woodpecker (Dryocopus pileatus) chicks in nest cavity, Troy, Montana

Donald M. Jones / Black-footed Ferret (Mustela nigripes) at night, UL Bend National Wildlife Refuge, north-central Montana

Donald M. Jones / Black-footed Ferret (Mustela nigripes) at night, UL Bend National Wildlife Refuge, north-central Montana

Donald M. Jones / Black-footed Ferret (Mustela nigripes) at night, UL Bend National Wildlife Refuge, north-central Montana

Tim Fitzharris / Cape Teal (Anas capensis) pair with chicks, Lake Bogoria, Kenya

Tom Vezo / Western Screech Owl (Megascops kennicottii) juvenile at nest, Green Valley, Arizona

Tom Vezo / Round-tailed Ground Squirrel (Spermophilus tereticaudus) in burrow, Arizona

Pete Oxford / Wasp (Polybia sp) constructing nest, Yasuni National Park, Amazon Rainforest, Ecuador

Tom Vezo / Red-tailed Hawk (Buteo jamaicensis) parent at nest with chicks, Arizona

Tom Vezo / Red-tailed Hawk (Buteo jamaicensis) parent at nest with chicks, Arizona

Tom Vezo / Red-necked Grebe (Podiceps grisegena) pair at nest, British Columbia, Canada

Tom Vezo / Red-necked Grebe (Podiceps grisegena) at nest with eggs, British Columbia, Canada

Tom Vezo / Northern Cardinal (Cardinalis cardinalis) female removing fecal sac from nest near chicks, Green Valley, Arizona

Tom Vezo / Northern Cardinal (Cardinalis cardinalis) father and chicks in nest, Green Valley, Arizona

Tom Vezo / Mountain Bluebird (Sialia currucoides) male at nest box, British Columbia, Canada

Tom Vezo / Little Blue Heron (Egretta caerulea) on nest, Rio Grande Valley, Texas

Tom Vezo / Little Blue Heron (Egretta caerulea) on nest, Rio Grande Valley, Texas

Tom Vezo / Little Blue Heron (Egretta caerulea) on nest, Rio Grande Valley, Texas

Tom Vezo / Horned Grebe (Podiceps auritus) male with chicks on nest, Saskatchewan, Canada

Tom Vezo / Horned Grebe (Podiceps auritus) male with chick on nest, Saskatchewan, Canada

Tom Vezo / Harris' Hawk (Parabuteo unicinctus) parent in nest with chicks, Texas

Tom Vezo / Great Egret (Ardea alba) pair in nest, Florida

Tom Vezo / Great Egret (Ardea alba) pair in nest in breeding plumage, Florida

Tom Vezo / Great Blue Heron (Ardea herodias) parent displaying to protect chick in nest, Venice Rookery, Florida

Tom Vezo / Great Blue Heron (Ardea herodias) parent in nest with chicks, Venice Rookery, Florida

Tom Vezo / Great Blue Heron (Ardea herodias) on nest, Venice Rookery, Florida