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Arctic tern

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The Arctic tern (*Sterna paradisaea*) is a medium-sized seabird within the family Laridae. These birds are famous for performing the longest migrations known in the animal kingdom. By traveling between the Arctic and the Antarctic, they experience two summers every year. This unique lifestyle allows them to see more daylight than any other creature on Earth.

2009 07 02 - Arctic tern nesting on Farne Islands
2009 07 02 - Arctic tern nesting on Farne Islands

The mechanism of their migration is a complex, winding journey. Rather than flying in a straight line, Arctic terns follow a convoluted route. They do this to take advantage of prevailing winds. This strategy makes their massive travels more efficient. Recent studies show that previous estimates of their travel distance were too low. Scientists now know these birds take meandering courses instead of direct paths.

Arctic terns have specific physical traits that aid their lifestyle. They weigh approximately 100 grams and have a wingspan of about 1 meter. Their length ranges from 30 to 40 centimeters. During the breeding season, they have grey and white plumage. They also possess a blood-red beak and red webbed feet. A black crown and nape decorate their heads. In the winter, their bills and legs turn black.

2009 07 02 - Arctic tern nesting on Farne Islands
2009 07 02 - Arctic tern nesting on Farne Islands

Research has revealed staggering distances covered by individual birds. For example, a bird from the Farne Islands named 'G82' traveled 90,000 kilometers in just ten months. This journey included crossing the Atlantic and Indian Oceans. It even reached the South Pacific near the Ross and Amundsen Seas. Other birds nesting in Iceland or Greenland cover 70,000 to 90,000 kilometers annually. Over a 30-year lifetime, a tern may travel the equivalent of three round trips to the Moon.

2009 07 02 - Arctic tern nesting on Farne Islands
2009 07 02 - Arctic tern nesting on Farne Islands

The life cycle of the Arctic tern involves intense parental care. They are K-selected species, meaning they live long lives and raise few young. They mate for life and often return to the same colony each year. Courtship includes "high flights" and "fish flights" where males offer food to females. They nest in simple ground depressions. Both parents share the duty of incubating the eggs. The chicks are precocial, meaning they can move within days of hatching.

Arctic terns are highly aggressive defenders of their nests. They will attack humans and large predators like foxes or cats. They often strike at the top or back of a predator's head. This behavior protects their one to three eggs per clutch. Their diet consists mainly of small fish like herring, cod, and capelin. They also eat marine invertebrates such as krill, crabs, and amphipods. Sometimes they even engage in kleptoparasitism, which is stealing food from other birds.

2009 07 02 - Arctic tern nesting on Farne Islands
2009 07 02 - Arctic tern nesting on Farne Islands

There are approximately two million Arctic terns in the world. Most of this population lives in Europe. While the species is currently evaluated as a "least concern" by the IUCN, numbers have faced challenges. In the late nineteenth century, hunting for the millinery trade reduced populations in New England. Exploitation also continues in western Greenland. Understanding their migration helps scientists protect these vital migratory waterbirds.

2009 07 02 - Arctic tern nesting on Farne Islands
2009 07 02 - Arctic tern nesting on Farne Islands
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