Auks are the penguins of the Northern Hemisphere, except that they can fly. The family includes puffins, murres (called guillemots in Britain), razorbills, auklets and murrelets, about 25 species in all. The Atlantic puffin pictured is 10-12 inches (25-30 cm) long and weighs about 1 lb (450 g); the largest living auks, the murres, reach 18 inches (45 cm).
Auks have stocky bodies, short wings and black-and-white plumage. They fly fast and straight with whirring wingbeats, and underwater they use those same wings to "fly" after fish, diving to 200 feet (60 m) and, in the case of murres, more than 600 feet (180 m).
The puffin's colourful bill plates grow for the breeding season and are shed in autumn, leaving a much duller winter face.
Auks live in the cold waters of the North Atlantic and North Pacific, from the Arctic south to California, Japan, Britain and New England. They spend the winter far out at sea.
In summer they gather in huge colonies on sea cliffs and islands. Murres pack shoulder to shoulder on bare ledges, while puffins dig burrows in the turf on top of the cliffs.
Auks eat small fish such as sand eels, capelin and herring, along with crustaceans and squid. A puffin can hold a dozen or more small fish crosswise in its bill at once, gripping them against spines on its palate while it catches more.
Auks nest in dense colonies and most lay a single egg. A murre's egg is sharply pointed so it rolls in a tight circle rather than off the ledge. Murre chicks leap from the cliffs at three weeks old, before they can fly, and finish growing at sea with their fathers.
Pairs often mate for life and return to the same burrow or ledge each year. Puffins greet each other by rubbing bills together, a display called billing.
The auk family Alcidae includes the Atlantic puffin, horned and tufted puffins, common and thick-billed murres, the razorbill, little auk and many small auklets and murrelets. The flightless great auk, once common across the North Atlantic, was hunted to extinction in 1844.
The IUCN lists the Atlantic puffin as Vulnerable after steep declines in Iceland and Norway. Overfishing of the small fish auks depend on, warming seas, oil spills, gill nets and introduced predators on nesting islands are the main threats.
