An auk is a bird of the family Alcidae in the order Charadriiformes. Extant auks range in size from the least auklet, at 85 g (3oz) and 15cm (5.9in), to the thick-billed murre, at 1kg (2.2lb) and 45cm (18in). They are good swimmers and divers, but their walking appears clumsy. Modern auks can fly (except for the extinct great auk). Due to their short wings, auks have to flap their wings very quickly in order to fly.