Arctic tern

Arctic tern
Name	Arctic tern
Status	LC
Status system	IUCN3.1
Genus	Sterna
Species	paradisaea
Authority	Pontoppidan, 1763

Arctic tern. The Arctic tern is a medium-sized seabird in the family Laridae, renowned for undertaking the longest known annual migration of any animal. It breeds in the Arctic and subarctic regions of Europe, Asia, and North America before traveling to the Southern Ocean for the austral summer. This incredible journey ensures the bird experiences two summers each year and sees more daylight than any other creature on Earth.

Description

The Arctic tern is a slender, graceful bird with long, pointed wings and a deeply forked tail. In breeding plumage, it has a black cap, a blood-red bill, and short red legs, with a pale gray mantle and white underparts. The species is often confused with the closely related Common tern, but can be distinguished by its uniformly gray tail streamers and shorter legs. Non-breeding adults and juveniles show a black bill, a white forehead, and darker primaries. Its flight is buoyant and agile, a characteristic shared with other members of the genus Sterna.

Distribution and habitat

During the boreal summer, the Arctic tern nests on coastal beaches, islands, and tundra across the northern reaches of the Northern Hemisphere. Key breeding colonies are found in Iceland, Greenland, Svalbard, northern Scandinavia, Siberia, Alaska, and the Canadian Arctic Archipelago. Outside the breeding season, it is entirely pelagic, inhabiting the open ocean. Its wintering grounds encompass the pack ice and rich waters of the Antarctic region, particularly the Weddell Sea and areas near the Antarctic Peninsula.

Migration

The migration of the Arctic tern is an extraordinary feat of endurance, with individuals routinely traveling over 70,000 kilometers round-trip annually. Birds from Greenland and Iceland often fly south across the Atlantic Ocean, down the coast of West Africa, and then east across the Indian Ocean. Populations from the Pacific fly down the coasts of North America and South America or across the Pacific Ocean. Research using geolocator tags has documented these epic routes, which largely follow prevailing wind systems to conserve energy. The journey allows them to exploit the perpetual summer and abundant food resources at both poles.

Diet and feeding

The diet consists primarily of small fish, such as sand lance and capelin, and crustaceans, including krill and amphipods. It typically feeds by plunge-diving from the air, often hovering briefly before striking the water's surface. The species also engages in kleptoparasitism, harassing other seabirds like puffins or auks to steal their catch. During the breeding season, foraging occurs relatively close to colonies, but in winter, it feeds in the nutrient-rich upwelling zones of the Southern Ocean.

Reproduction and life cycle

Arctic terns arrive at breeding colonies in May or June, forming dense, noisy colonies. They are monogamous and often return to the same site annually. Nests are simple scrapes in the ground, sometimes lined with vegetation or pebbles. The typical clutch is one to three eggs, which are incubated by both parents for about three weeks. Chicks are semi-precocial and fledge after 21–28 days, though they remain dependent on parents for food for some time. They reach sexual maturity at three to four years of age and have been known to live over 30 years, as recorded by long-term studies on the Farne Islands.

Conservation status

The International Union for Conservation of Nature lists the Arctic tern as Least Concern globally. However, many local populations are declining due to threats such as habitat loss from coastal development, human disturbance at breeding sites, and reduced food availability from climate change and overfishing. Predation by invasive species like the American mink on islands is also a significant problem. Conservation efforts are focused on protecting key breeding colonies, such as those managed by the Royal Society for the Protection of Birds in the United Kingdom.

Category:Birds of the Arctic Category:Birds of the Antarctic Category:Migratory birds