Auks

Auks are penguinlike seabirds found in the Northern Hemisphere. These birds spend most of their lives in the coastal waters north of 25°N latitude, coming ashore only to lay their eggs and raise their young. There are 22 species of auks, including the Atlantic puffin, the common murre, the dovekie or lesser auk, and the extinct great auk.

Called alcids, the members of the auk family fill an ecological niche similar to that filled by the penguins in the southern hemisphere. However similar their role, the penguins and alcids are not closely related, the alcids being more closely related to the gulls.

Like penguins, alcids have waterproof feathers and swim and dive for their prey. Unlike penguins, auks can fly. Their wings are relatively small, and while auks are not especially graceful in flight, they are able to "fly" gracefully underwater in pursuit of prey. Auks obtain all of their food from the sea. Some of the smaller species subsist on plankton alone, but most eat fish. Like penguins, auks have deceptive coloration; when in Razor-billed auks (Alca torda). Photograph by J.L. Lepore. Photo Researchers, Inc. Reproduced by permission.
water, their white fronts make them nearly invisible to fish below.

Auks' legs are near the rear of their bodies, giving them an upright, penguinlike posture. In some species the feet and bill are brightly colored-most notably in the Atlantic puffin, whose blue, yellow, red, and white striped bill is important to the species during the mating season. The colorful plates that make up the harlequinesque bill are shed when the bird molts. Other species, such as the rhinoceros auklet, grow special tufts of feathers during mating season. Auks mate for life and are generally monogamous, although males will attempt to copulate with a female if she is not attended by her mate.

Most auks lay their eggs on bare stone ledges, or scoop out a nest in a burrow. An exception is the marbled murrelet, which builds a simple nest in the branches of seaside pines. Depending on the species, one or two eggs are laid and incubated for 29-42 days.

A few auk species breed in solitary pairs, but most congregate in large colonies. One of the most densely populated auk colonies on record included 70 pairs of common murres in a space of 7.5 sq ft (0.65 sq m). In species that congregate in such large rookeries, each bird's egg is uniquely colored and/or patterned, allowing for easy identification. Chicks, too, are recognized individually by their voice; chicks and parents start getting to know each other's voice even before hatching. Such recognition ensures that each auk feeds only its own offspring.

Chick development varies greatly among the auks. The young of the tiny ancient murrelet take to sea with their parents just a day after they hatch. Other species brood their chicks for 20-50 days. In general, smaller auks lay proportionately larger eggs, from which hatch more precocious chicks. For example, the ancient murrelet weights just over 0.7 oz (200 g), but lays an egg that is approximately one-fourth of the adult's body weight. The chicks reach sexual maturity in about three years.

Auks are long-lived; some birds banded as adults have been found in breeding colonies 20 years later. Their natural enemies include the great skua, the gyrfalcon, and the peregrine falcon.

Although auks are protected by law in North America, humans remain their greatest threat. In the 1500s, sailors slaughtered huge numbers of great auks for food on long sea voyages. Flightless and 2 ft (0.6 m) tall, the great auk was helpless when caught on land. Tens of millions of these birds were killed until the species became extinct in 1844, when the last great auk was killed on Eldez Island, off the coast of Iceland. More recently, hunting of other auk species has become a popular sport in Greenland.

Oil pollution—both from spills and from tanker maintenance—also kills countless birds each year. Oil destroys the waterproof quality of the auks' feathers and is swallowed by the birds when they attempt to clean themselves. Auk drownings in fishermen's gill nets have decreased in recent years. However, the decline in food-fish species such as cod and haddock have led fishermen to turn their attention to the fish species auks eat, such as sprats. Such competition does not bode well for the auks.