(Part of the) common name of species of the family Alcidae (Charadriiformes, suborder Alcae) and in the plural the general term for the family and suborder. Other common names used for (groups of) species are 'auklet', 'guillemot', 'murre' and 'puffin'. The Alcidae are wing-propelled diving birds inhabiting the colder parts of the northern oceans. They are rather 'chunky' birds of small to large size (15 to 75 cm long) with short tail and legs, and fully webbed toes (the first of the four toes is degenerated). The wings are also short and more or less pointed. In all but a few species (genera Pinguinus and Aethia) the flight feathers are moulted simultaneously, leading to a short period of flightlessness. The plumage is predominately black, grey and white. Auks are mainly pelagic, remaining at sea except for breeding. Their diet consists almost entirely of fish and marine invertebrates which are usually obtained by under-water pursuit (a few forms are bottom-feeders). See also: puffins.

Alternative forms for auks : Alca, Alle, auk, Cepphus, Uria.