Arctic tern

The genus name Sterna is derived from Old English "stearn", "tern". The specific paradisaea is from Late Latin paradisus, "paradise". The Scots names pictarnie, tarrock and their many variants are also believed to be onomatopoeic, derived from the distinctive call. Due to the difficulty in distinguishing the two species, all the informal common names are shared with the Common tern. == Distribution and migration ==

The Arctic tern has a continuous worldwide circumpolar breeding distribution; there are no accepted subspecies. It can be found in coastal regions in cooler temperate parts of North America and Eurasia during the northern summer. During the southern summer, it can be found at sea, reaching the northern edge of the Antarctic ice. The difference from previous estimates is due to the birds taking meandering courses rather than following a straight route as was previously assumed. The birds follow a somewhat convoluted course in order to take advantage of prevailing winds. A 2013 tracking study of half a dozen Arctic terns breeding in the Netherlands Arctic terns usually migrate sufficiently far offshore that they are rarely seen from land outside the breeding season. == Description and taxonomy ==

The Arctic tern is a medium-sized bird around from the tip of its beak to the tip of its tail. The wingspan is . The weight is . The beak is dark red, as are the short legs and webbed feet. Like most terns, the Arctic tern has high aspect ratio wings and a tail with a deep fork. The adult plumage is grey above, with a black nape and crown and white cheeks. The upperwings are pale grey, with the area near the wingtip being translucent. The tail is white, and the underparts pale grey. Both sexes are similar in appearance. The winter plumage is similar, but the crown is whiter and the bills are darker. Juveniles differ from adults in their black bill and legs, "scaly" appearing wings, and mantle with dark feather tips, dark carpal wing bar, and short tail streamers. During their first summer, juveniles also have a whiter forecrown. The species has a variety of calls; the two most common being the alarm call, made when possible predators (such as humans or other mammals) enter the colonies, and the advertising call. While the Arctic tern is similar to the Common and Roseate terns, its colouring, profile, and call are slightly different. Compared to the common tern, it has a longer tail and mono-coloured bill, while the main differences from the roseate are its slightly darker colour and longer wings. The Arctic tern's call is more nasal and rasping than that of the common, and is easily distinguishable from that of the roseate. This bird's closest relatives are a group of South Polar species, the South American (Sterna hirundinacea), Kerguelen (S. virgata), and Antarctic (S. vittata) terns. The immature plumages of Arctic tern were originally described as separate species, Sterna portlandica and Sterna pikei. == Reproduction ==

Breeding begins around the third or fourth year. and smaller mammalian predators such as foxes and cats. The nest is usually a depression in the ground, which may or may not be lined with bits of grass or similar materials. The eggs are mottled and camouflaged. Both sexes share incubation duties. The young hatch after 22–27 days and fledge after 21–24 days. If the parents are disturbed and flush from the nest frequently the incubation period could be extended to as long as 34 days. When hatched, the chicks are downy. Being precocial, the chicks begin to move around and explore their surroundings within one to three days after hatching. Usually they do not stray far from the nest. Chicks are brooded by the adults for the first ten days after hatching. Both parents care for hatchlings. Chick diets always include fish, and parents selectively bring larger prey items to chicks than they eat themselves. Males bring more food than females. Feeding by the parents lasts for roughly a month before being weaned off slowly. After fledging, the juveniles learn to feed themselves, including the difficult method of plunge-diving. They will fly south to winter with the help of their parents. Arctic terns are long-lived birds that spend considerable time raising only a few young, and are thus said to be K-selected. A 1957 study in the Farne Islands estimated an annual survival rate of 82%. Eidersperrwerk 18.05.2013 13-19-06.jpg|Nesting with an egg|alt=One tern nesting with an egg in Schleswig-Holstein, Germany Juvenile Arctic Tern.jpg|chick Arctic tern (Sterna paradisaea) adult with juvenile Flatey.jpg|adult with juvenile Arctic tern (Sterna paradisaea) juvenile Flatey.jpg|juvenile == Ecology and behaviour ==

The diet of the Arctic tern varies depending on location and time, but is usually carnivorous. In most cases, it eats small fish or marine crustaceans. While feeding, Skuas, gulls, and other tern species will often harass the birds and steal their food. Arctic tern (Sterna paradisaea) in flight Myrar.jpg|adult Arctic tern (Sterna paradisaea) with eel Blonduos.jpg|with an eel Arctic tern (Sterna paradisaea) hovering with food over nest Flatey.jpg|hovering with food over nest Arctic tern (Sterna paradisaea) attacking, Amsterdam island, Svalbard.jpg|defending its offspring Arctic tern (Sterna paradisaea) juvenile in flight Blonduos.jpg|juvenile == Conservation status ==

The total population for the arctic tern is estimated at more than two million individuals, with more than half of the population in Europe. The breeding range is very large, and although the population is considered to be decreasing, this species is evaluated as a species of least concern by the IUCN. At the southern part of their range, the Arctic tern has been reducing in numbers. Much of this is due to a lack of food. and its ability to feed in its Antarctic wintering is dependent on sea-ice cover, but unlike breeding species, it is able to move to a different area if necessary, and can be used as a control to investigate the effect of climate change on breeding species. == Cultural depictions ==

The Arctic tern has appeared on the postage stamps of several countries and dependent territories. The territories include Åland, Alderney, and Faroe Islands. Countries include Canada, Finland, Iceland, and Cuba. In the sketch, Colin alluded the call of the Arctic tern to sounding like the band name Backstreet Boys. A European constellation of weather satellites on polar orbits is named EPS-Sterna in reference to the bird's long migrations. == References ==