Arctic tern

Arctic tern (Sterna paradisaea).

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Arctic tern, (Sterna paradisaea), tern species that makes the longest annual migration of any bird. It breeds in the southerly reaches of the Arctic and winters in the Antarctic, making its migration a round-trip of 60,000 to 82,000 km (roughly 37,000 to 51,000 miles). Its appearance—white with a black cap and grayish wings—is similar to that of the common tern (Sterna hirundo), its frequent companion.