36-43 cm (14-17") Common in Arctic on tundra lakes, rivers, coasts; winters at sea to Antarctic. Graceful, pigeon-sized bird with a very long forked tail. White head with a black cap; all-red bill; grayish underparts with translucent primaries; pale uniformly gray mantle; short red legs. Similar Common Tern has a black-tipped bill; whiter underneath with no translucent primaries.
Winter adult similar, but black cap is incomplete; bill and feet blackish.
Song: harsh "kee-urr".