An auk is a seabird with a heavy body and short tail. Any of several diving sea birds (family Alcidae) of northern regions, such as the razor-billed auk, having a chunky body, short wings, and webbed feet. a black and white seabird with short wings (alk, alka, from alka). In general, any of 22 species of diving birds (family Alcidae), especially the little auk and the razorbill, or razor-billed auk. Auks are 6-16 in. (15-40 cm) long, with short wings and legs and webbed feet. They occur only in Arctic, subarctic, and temperate regions (with a few species south to Baja California). Auks nest colonially on cliff ledges or in rock crevices or burrows near the sea; many spend the winter far from land. They feed on fish, crustaceans, mollusks, and plankton. True auks are black and white and stand erect on land. See also great auk