Auks

views updated May 11 2018

Auks

Resources

Auks are penguin-like 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 23 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 (Alcidae) 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 are more closely related to the gulls.

Like penguins, alcids have waterproof feathers and swim and dive for their prey. Their wings are relatively small, but, unlike penguins, while auks are not especially graceful in flight they can fly. They are also 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 water, their white fronts make them nearly invisible to fish below.

Auks legs are near the rear of their bodies, giving them an upright, penguin-like posture. In some species, the feet and bill are brightly coloredmost 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 2942 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 birds 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 others voices 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 2050 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 adults 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 gyr-falcon, 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 pollutionboth from spills and from tanker maintenancealso 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 fishermens gill nets have decreased in recent years. However, the decline in food-fish species such as cod and haddock has led fishermen to turn their attention to the fish species auks eat, such as sprats. Such competition does not bode well for the auks.

Resources

BOOKS

Brooke, M., and T. Birkhead, editors. The Cambridge Encyclopedia of Ornithology. Cambridge: Cambridge University Press, 1991.

Forshaw, Joseph. Encyclopedia of Birds. 2nd ed. New York: Academic Press, 1998.

Terres, John K. The Audubon Encyclopedia of North American Birds. Avenel, NJ: Wings Books, 1995.

F.C. Nicholson

Auks

views updated Jun 08 2018

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
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.


Resources

books

Brooke, M., and T. Birkhead, eds. The Cambridge Encyclopedia of Ornithology. Cambridge: Cambridge University Press, 1991.

Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.

Terres, John K. The Audubon Encyclopedia of North AmericanBirds. Avenel, NJ: Wings Books, 1991.


F.C. Nicholson

Alcidae

views updated May 29 2018

Alcidae (auks; class Aves, order Charadriiformes) A family of mainly black and white, small-winged, diving seabirds in which the legs are set well back, the feet are webbed, and bills vary from long and pointed to laterally compressed and high. Auks are mainly pelagic and gregarious, breeding in burrows or crevices, or on open cliff ledges, usually colonially. Brachyramphus marmoratus (marbled murrelet) breeds on forest branches. The two species of Fratercula (puffins) have distinctive yellow and red, large, laterally compressed bills during the breeding season; the horny bill plates and a horn-like structure around the eye are both shed in winter. Their feet are red with claws modified for digging burrows; they inhabit grassy island slopes and cliffs, breeding in rock crevices and burrows, and spending the rest of the year at sea. Auks feed on fish and invertebrates. There are 12–14 genera, and 22 species, found in northern regions of the Pacific and Atlantic, and in the Arctic.

auks

views updated May 21 2018

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