Auk, the name of certain sea birds of the family alcadce, including the subgenera alca, fratercula, mergulus, and phaleris. The true auks (alca) are strictly ocean birds, and scarcely ever leave the water, except to build their nests and breed in immense flocks in caverns and crannies of rocks, laying one disproportionately large egg. The young are fed from the crops of their parents, even after they can move about freely and shift for themselves. This genus contains but two species, the great auk and the razor bill. The former (A. impennis, Linn.) is remarkable for the imperfect development of its wings, which are totally unfit for flying. They are set very far back on the body, and not much more than rudimental; but they are used by the bird as oars, and in conjunction with its feet it plies them with such power and velocity that it has been known to escape from a six-oared barge pulled by vigorous oarsmen. It rarely leaves the arctic circle and the waters adjoining, nor is it often seen off soundings, but dwells in great numbers about the Faro islands and Iceland, and it has been asserted that it breeds in Newfoundland. In summer all the upper parts of this bird's plumage are of a deep sooty black, which is changed in winter to white on the cheeks, the sides of the neck, and the throat.

It breeds in June and July, and lays one large yellowish egg, as big as a swan's, irregularly dashed with black marks, which have been compared to Chinese characters. It has a large decurved bill with sharp cutting edges; and its feet being situated at the extremity of its body, it stands or sits erect, propped up by its short stiff tail, after the manner of the penguins, which it not a little resembles. - The black-billed auk, razor bill, or murre (A. torda, Linn.) belongs to the northern latitudes, in the extreme height of which these birds swarm in multitudes during the breeding season, affording food and clothing to the Esquimaux, who place on them their chief dependence. The bill of the black auk has a sharp hook at its extremity, and a denticulated process at about two thirds of its length, which is of great use in securing its slippery prey. Its general color is dusky above and white below; it flies sufficiently well, but, like the species last described, uses its wings as oars in diving, which it does to perfection.

It is very abundant on all the rocky coasts of Great Britain, where it sits in long horizontal rows on the steps or ledges of the crags, towering one above the other. - The genus fratercula consists of a single species, the Labrador auk, common puffin, or coulter-neb (F. arctica), this last name being admirably descriptive of its strong massive beak, the mandibles of which, when separated, especially the upper one, almost exactly resemble the coulter of a plough. The upper parts of this bird are dusky, its cheeks and belly white. It has a black collar, legs and feet orange, beak broad, cutting-edged, bluish gray next to the head, but scarlet thence to its obtuse point. Although it extends to the high arctic regions, it is in England only a summer visitor, breeding in the low sandy islands in rabbit burrows, of which it dispossesses their legitimate owners; or, where there are no rabbits, burrowing itself. In rocky places, as Dovor cliffs, Flamborough head, and the Bass rock, at all which places these birds abound, they lay their single egg in the crevices of the rocks. When they have reared their young, they pass from England to the southern coasts of France and Spain, where they winter.

Their burrows are curiously excavated, by means of their bills, to the depth of two or three feet, and often have two entrances for escape in case of surprise. The length of the puffin is about 12 inches. - The mergulus has likewise but one representative, the little auk, common rotche, or sea dove (M. melanoleucos), which is the smallest of the family, and a native of the very highest latitudes, congregating in large flocks near the arctic circle; Greenland, Spitzbergen, and Melville island being its favorite stations. Its plumage is black and white; and in winter the front of the neck, which is black in summer, turns white. It lays but a single egg, of pale bluish green, on the most inaccessible ledges of the precipices which overhang the ocean. It is about 9 or 10 inches long. - The last division, phaleris, contains also but a single species, the paroquet auk (P. psittacula), an extreme northern bird, about 11 inches long. Its head, neck, and upper parts are black, blended into ash color on the forward parts of the neck; the breast and belly white; the legs are yellowish, the beaks in the adults red. This bird swims and dives admirably, and is said to be of a singularly unsuspicious character, and easily captured.

About midsummer it lays one large egg, nearly of the size of a hen's, with brown or dusky spots, on a whitish or yellowish ground.

Great Auk (Alca impennis).