Arctic Tern

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The Arctic Tern (Sterna paradisaea) is a tern. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe. The species is migratory, seeing two summers each year as it migrates to the Antarctic coast for the southern summer and then back again about six months later. These are the longest migrations known in the animal kingdom. The Arctic tern nests once every one to three years 
Arctic terns are medium-sized birds. They are mainly grey and white plumaged, with a red/orange beak and feet, white forehead, a black nape and crown (streaked white), and white cheeks. 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.
Distribution and migration
The Arctic Tern 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 Arctic tern is famous for its migration; it flies from its Arctic breeding grounds to the Antarctic and back again each year.
Description
The Arctic tern is a medium-sized bird The beak is dark red, as are the short legs and webbed feet.
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. 
The species has a variety of calls; the two most common being the alarm call, made when predators (such as other mammals) enter the colonies, and the advertising call.
Reproduction
Breeding begins around the third or fourth year. Arctic terns mate for life and return to the same colony each year.
Mating occurs shortly after this. Breeding takes place in colonies on coasts, islands and in land on tundra near water. It lays from one to three eggs, most often two.
It is one of the most aggressive terns, defensive of its nest and young. It will attack large predators, striking the top or back of the head. It is capable of repelling many raptorial birds, polar bears and smaller mammal predators such as foxes and cats.
The nest is usually a depression in the ground. The eggs are mottled and camouflaged. The young hatch after 22–27 days and fledge after 21–24 days.
When hatched, the chicks are downy. 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 include fish, and parents bring larger prey to chicks than they eat themselves. Males bring more food than females. After fledging, the juveniles learn to feed themselves. They will fly south to winter with the help of their parents.
Behaviour
The diet of the Arctic tern is carnivorous. It eats Fish or Crustaceans. The Crustaceans eaten are Amphipods, Crabs and Krill. Sometimes, these birds also eat Molluscs, Worms, or Berries, and on their northern breeding grounds, Insects.
While nesting, Arctic terns are vulnerable to predation by cats and other animals. The larger Herring Gull steals eggs and hatchlings. Camouflaged eggs help prevent this, as do nesting sites. While feeding, Skuas, Gulls, and other Terns will often harass the birds and steal their food.