Bird of the Week: Arctic Tern
The Arctic tern is a “migratory marvel.”
In the current issue of National Wildlife, science writer Jessica Snyder Sachs reports that last year an international team of researchers employed geolocators—tiny animal-tracking devices—to follow the journeys of these seabirds as they made their way back and forth between wintering grounds off Antarctica and breeding grounds in the Arctic. The scientists discovered that the birds migrate the longest distance of any animal: close to 50,000 miles a year, or the equivalent of 3 journeys to the moon and back over a tern’s roughly 30-year lifetime.
During their long migrations, Arctic terns spend most of the time far out at sea and are rarely spotted from shore. Studying the birds is challenging, but scientists have learned that they feed on a wide variety of small fish, crustaceans and other invertebrates—and will also catch insects on the wing. According to the Cornell Lab of Ornithology, the terns capture their marine prey by plunging into the water; before diving, they may hover briefly in mid-air.
Long-lived birds, Arctic terns do not start breeding until they are about three or four years old. The species’ breeding range circles the entire globe, but most birds return to nest in the area where they hatched—either in tundra or boreal forests or on rocky islands and beaches. The terns’ nests consist of scrapes in gravel or grass, or of platforms of vegetation or debris, and are placed on the ground out in the open.
Fluffy Arctic tern chicks may be either gray or brown. Within the same nest, chicks can come in both colors.
In the United States, you can spot Arctic terns in Alaska and off the coast of New England during the breeding season as far south as Cape Cod, Massachusetts. During the 19th Century, North Atlantic populations declined because the birds were hunted heavily for the plume trade. The species recovered from this onslaught, but populations once again are falling in some parts of New England, according to the Cornell lab. The reasons are not yet known.
Voice: Similar to the common tern–varied high, grating calls, including a quick kik, a rising krrrrri (often in rapid series), a squeaky kirrIH and a harsh KRII-ah–but higher, harsher and less musical.
Sources: “Migratory Marvels” by Jessica Snyder Sachs, National Wildlife, April/May 2011, Cornell Lab of Ornithology’s All About Birds, Cornell Lab of Ornithology’s The Birds of North America Online and National Wildlife Federation Field Guide to Birds of North America.
Find out about the long-distance feats of other migratory birds, including the bar-tailed godwit, red knot and ruby-throated hummingbird.
Learn how you can help migratory birds at home.
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