Arctic Terns are medium-sized birds. They have a length of 33-39 cm (13-15 in) and a wingspan of 76-85 cm (26-30 in). They are mainly grey and white plumaged, with a red beak (as long as the head, straight, with pronounced gonys) and feet, white forehead, a black nape and crown (streaked white), and white cheeks. The grey mantle is 305 mm, and the scapulae are fringed brown, some tipped white. The upper wing is grey with a white leading edge, and the collar is completely white, as is the rump. The deeply forked tail is whitish, with grey outer webs. The hindcrown to the ear-coverts is black. Arctic Terns are long-lived birds, with many reaching thirty years of age.
Habitat and Distribution
This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe, Asia, and North America (as far south as Brittany and Massachusetts). The species is strongly migratory, seeing two summers each year as it migrates from its northern breeding grounds along a winding route to the oceans around Antarctica and back, a round trip of about 70,900 km (c. 44,300 miles) each year. This is by far the longest regular migration by any known animal. The Arctic Tern flies as well as glides through the air, performing almost all of its tasks in the air.
They eat mainly fish and small marine invertebrates. Arctic Terns sometimes dip down to the surface of the water to catch prey close to the surface. They may also chase insects in the air when breeding.
It nests once every one to three years (depending on its mating cycle); once it has finished nesting it takes to the sky for another long southern migration. The eggs are mottled and camouflaged. Both sexes share incubation duties. The young hatch after 22-27 days and fledge after 21-24 days. When hatched, the chicks are downy.
Calls and Songs
The species has a variety of calls; the two most common being the alarm call, made when possible predators enter the colonies, and the advertising call. The advertising call is social in nature, made when returning to the colony and during aggressive encounters between individuals. It is unique to each individual tern and as such it serves a similar role to the bird song of passerines, identifying individuals.