Southern elephant seal (Mirounga leonina) bull rules the harem during breeding season, Sea Lion Island, Falkland Islands, South America

Rockhopper penguins (Eudyptes chrysocome) mate during breeding season, Sea Lion Island, Falkland Islands, South America

Gentoo penguins (Pygoscelis papua) mate during breeding season, the Neck, Saunders Island, Falkland Islands, South America

Adult black-legged kittiwakes (Rissa tridactyla) feeding at the base of a glacier in the Svalbard Archipelago, Norway, Arctic, Europe

Adult black-legged kittiwakes (Rissa tridactyla) on ice near Alexander Island in Franz Josef Land, Russia, Arctic Ocean, Eurasia

King penguins (Aptenodytes patagonicus) at breeding and nesting colony at Salisbury Plain in the Bay of Isles, South Georgia, Polar Regions

A Little Egret (Egretta garzetta), during the breeding season, on Brownsea Island, a nature reserve in Poole Harbour, Dorset, England, United Kingdom, Europe

Adult Swallow-Tailed Gull, showing breeding season red rimmed eye, a nocturnal equatorial seabird, found almost exclusively in the Galapagos Islands, UNESCO World Heritage Site, Ecuador, South America

Adelie penguins (Pygoscelis adeliae), at breeding colony at Brown Bluff on the eastern side of the Antarctic Peninsula, Antarctica, Polar Regions

A gentoo penguin (Pygoscelis papua) breeding colony on Pleneau Island in early season, Antarctica, Polar Regions

Female mallard duck with newly hatched ducklings, Anas platyrhynchos, on a stream in springtime at Swinbrook, the Cotswolds, UK

Female mallard duck with 14 newly hatched ducklings, Anas platyrhynchos, on a stream in springtime at Swinbrook, the Cotswolds, UK

Female mallard duck with new ducklings, Anas platyrhynchos, strolling on garden patio in springtime at Swinbrook, the Cotswolds, UK

Female Canada Goose, Branta canadensis, with young goslings, on River Windrush at Swinbrook, the Cotswolds, UK

Moorhen's nest, with seven eggs laid, made with twigs among iris plants in a pond in Swinbrook, the Cotswolds, Oxfordshire, UK

Moorhen's nest, with seven eggs laid, made with twigs among iris plants in a pond in Swinbrook, the Cotswolds, Oxfordshire, UK

Lamb suckling from its mother, the Cotswolds, Oxfordshire, United Kingdom, UK.

Sheep and lamb in buttercup meadow, Taynton, The Cotswolds, Oxfordshire

Moorhen's nest, with seven eggs laid, made with twigs among iris plants in a pond in Swinbrook, the Cotswolds, Oxfordshire, UK

Lamb in Stanway, Gloucestershire, United Kingdom

Female mallard duck with new ducklings, Anas platyrhynchos, on a stream in springtime at Swinbrook, the Cotswolds, UK

Lambs in the Cotswolds, Oxfordshire, United Kingdom, UK.

Lambs in Stanway, Gloucestershire, United Kingdom

Four golden eggs in a nest

Masked Pufferfish (Arothron diadematus). Usually solo, seen here feeding on Acropora Sp. coral. Seen in large groups only during the breeding season. Found only in the Red Sea. Red Sea.

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult puffin (Fratercula arctica) during breeding season on Sumburgh Head, Shetlands, Scotland

Adult puffin (Fratercula arctica) during breeding season on tiny Grimsey Island, Iceland

Four golden eggs in a nest

Four golden eggs in a nest

Adult puffin (Fratercula arctica) during breeding season on Sumburgh Head, Shetlands, Scotland

Adult puffin (Fratercula arctica) during breeding season on tiny Grimsey Island, Iceland

Adult puffin (Fratercula arctica) during breeding season on Sumburgh Head, Shetlands, Scotland

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult puffin (Fratercula arctica) during breeding season on Sumburgh Head, Shetlands, Scotland

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult Weddell Seal (Leptonychotes weddellii) hauled out on ice near the Antarctic Peninsula, Southern Ocean

Adult puffin (Fratercula arctica) during breeding season on tiny Grimsey Island, Iceland

Masked Pufferfish (Arothron diadematus). Usually solo, seen here feeding on (Acropora Sp.) coral. Seen in large groups only during the breeding season. Found only in the Red Sea. Red Sea.

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult puffin (Fratercula arctica) during breeding season on tiny Grimsey Island, Iceland

Adult puffin (Fratercula arctica) during breeding season on tiny Grimsey Island, Iceland

Adult puffin (Fratercula arctica) during breeding season on tiny Grimsey Island, Iceland

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult puffin (Fratercula arctica) during breeding season on tiny Grimsey Island, Iceland

A blackbirds nest with four eggs

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Nest of oystercatcher (Haematopus ostralegus). This nest was in exactly the same position for two consecutive breeding seasons. Hebrides, Scotland.

Adult puffin (Fratercula arctica) during breeding season in Isfjardardjup, Northwestern Iceland

Polar Bear (Ursa maritimus) on sea ice off the sub-arctic coast of Hudson Bay, Churchill, Manitoba, Canada. Bears come to the coast of Hudson Bay in Fall waiting for the ice to freeze, and looking for a careless seal or dead whale to wash up. Global warming has shortened their winter so they are increasingly anxious as they wait for winter. While they wait, they engage in frequent wrestling matches to determine a mating hierarchy for the breeding season in March and April, and regularly check on the ice to see if it will carry them out to sea.

Male Frigate bird with red gular pouch that is inflated during the breeding season to attract a mate, Heart, Galapagos, Ecuador, South America

Southern elephant seal (Mirounga leonina) after harem and breeding season. Young bulls fighting and establishing pecking order. South America, Falkland Islands, January

Southern elephant seal (Mirounga leonina) after harem and breeding season. Young bulls fighting and establishing pecking order. South America, Falkland Islands, January

Southern elephant seal (Mirounga leonina) after harem and breeding season. Young bulls fighting and establishing pecking order. South America, Falkland Islands, January

Southern elephant seal (Mirounga leonina) after harem and breeding season. Young bulls fighting and establishing pecking order. South America, Falkland Islands, January

Southern elephant seal (Mirounga leonina) after harem and breeding season. Young bulls fighting and establishing pecking order. South America, Falkland Islands, January

Southern elephant seal (Mirounga leonina), old bull, after harem and breeding season on the Falkland Islands. South America, Falkland Islands, January

Close-Up Of Male Willow Ptarmigan Changing From Winter To Breeding Plumage Near Savage River, Denali National Park & Preserve, Interior Alaska, Spring

Portrait of a bull moose (Alces alces) walking through an alpine meadow late in the rut in Southcentral Alaska's Chugach State Park, Alaska, United States of America

Bull moose (Alces alces) pauses late in the rut in South-central Alaska's Chugach State Park, Anchorage, Alaska, United States of America

Approached by a cow moose, a bull (Alces alces), displays the Flehmen response late in the rut in Southcentral Alaska's Chugach State Park, Anchorage, Alaska, United States of America

Alaska bull moose (Alces alces) patrols a marsh during the rut, or fall breeding season, in mid-September, Anchorage, Alaska, United States of America

Close-up portrait of a male willow ptarmigan (Lagopus lagopus) showing early breeding colors in its neck and eye combs, surveying its high-country territory in Southcentral Alaska's Chugach Mountains on an April day. The head and neck will become completely chocolate-brown as the bird's breeding colors develop, Alaska, United States of America

Bull moose (Alces alces) wades through the mist of a cool Southcentral Alaska evening during the September 'rut', or breeding season. Moose are the largest member of the deer family. The animals are circumpolar and the Alaska-Yukon race, Alces alces gigas, is the largest of all, Alaska, United States of America

Bull moose (Alces alces) is startled as a jealous cow threatens a competitor during the rut, or breeding season, in Southcentral Alaska's Chugach State Park, USA, Alaska, United States of America

King eider duck (Somateria spectabilis) adult male in breeding plumage on winter ice floes during a snow shower in Varanger, Norway

Imperial Cormorant in breeding season, Falkland Islands

Imperial Cormorant in breeding season, Falkland Islands

Imperial Cormorant in breeding season, Falkland Islands

Common Ringed Plover (Charadrius hiaticula) in breeding season on a pebble beach in the Cotentin, Manche, Normandy, France

Adult breeding dolphin gull flying over imperial shags

Adult breeding dolphin gull, Falkland Islands