The Incredible Arctic Tern

The Arctic Tern (Sterna paradisaea) is an Arctic to Antarctic traveler with annual migrations of up to 24,000 miles round trip, the longest annual migration of any creature on Earth. On its wintering grounds, this Olympic flyer benefits from a “second summer”, giving it more hours of daylight than any other bird.

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In addition to excellent flying abilities, this slender tern is also known for its elegant breeding plumage. The bill, feet, and legs are blood-red. The upper wings and back are light gray, contrasting with a jet-black cap. The tail is long and deeply forked.

Nests of the Arctic Tern are commonly made near fresh or salt water in open, usually treeless environments. The nest is very difficult to spot unless it contains eggs; it is little more than a shallow depression scraped in the ground. Intruders in nesting areas are often met with aggressive dives and pecks on the back or head.

Diet varies from place to place, but fish is the primary food given to chicks. Prey is captured by plunge-diving or dipping. Occasionally insects are taken on the wing.

In Alaska, in addition to its’ wide breeding distribution on the arctic coastal plain of the Beaufort Sea, it nests along the coasts of the Chukchi and Bering Seas and on St. Lawrence Island. There are also breeding sites in the western Aleutian Islands and many sites throughout the Gulf of Alaska, some as far south as Southeast Alaska.

It is not known specifically where Arctic Terns from North America spend the winter, but birds from the entire northern hemisphere are thought to intermingle around Antarctica. Some birds also winter in southern Africa, southern Australia, and New Zealand.

There are no data for general population trends in Canada, Alaska, or on the Atlantic Coast, but declines have been reported within each of these areas. In the Gulf of Alaska, both coastal colony counts on Kodiak Island and surveys at sea in Prince William Sound indicated declines of more than 90%. Except for the effects of the 1964 earthquake in Alaska, factors causing the population decline and preventing population recovery are unknown.

Since Arctic Terns are long-lived, far-traveling, and spend part of their year at each pole, they may contribute valuable insights into numerous scientific questions about birds (e.g. daylight exposure and migration, accumulated environmental impacts, and abstention from breeding and movement as responses to changes in food supplies).

However, the Alaskan population is not monitored and there is a lack of knowledge about most aspects of their population. Very little is known about nonbreeders in the Antarctic and most of the mortality occurs during this part of the yearly cycle. Therefore, we need to begin with a better understanding of the species distribution, numbers, and trends throughout its range.

courtesy of U.S. Fish & Wildlife Service

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