Penguins are the most highly specialized of all birds for marine life.
They swim entirely by means of their flipperlike wings, using their webbed feet as rudders. Their stiff feathers serve as insulation, and are waterproof when oiled. Their chief enemies are the leopard seal, killer whale, and skua gull. The smaller jackass penguins, Spheniscus demersus, are named for their braying cry, and crested penguins are distinguished by yellow plumes on either side of the head. Smallest of all is the little blue penguin, Eudyptula minor, of New Zealand and Australia.