Auks, Puffins, and Murres (Alcidae)

(Alcidae)

Class: Aves

Order: Charadriiformes

Suborder: Alcae

Family: Alcidae

Thumbnail description
Small to medium-sized marine diving birds with short, narrow wings, short tails, and a great variety of bill shapes and sizes

Size
6–18 in (12–45 cm): 0.17–2.4 lb (80 g–1.1 kg)

Number of genera, species
13 genera: 23 species

Habitat
Oceans, shorelines, and islands

Conservation status
Extinct: 1 species; Vulnerable: 4 species

Distribution
Circumpolar distribution in North Atlantic, North Pacific, and Arctic oceans

Evolution and systematics

The auks are quite different, both in appearance and behavior, from all other waders and gull-like birds. Although the alcids have been associated with several different families in the last century—penguins (Spheniscidae) and grebes (Podicipedidae) among them—current taxonomy leaves Alcidae in a separate suborder of the Charadriiformes. The predominance of species that breed in the North Pacific indicates that the family's ancestry may lie in that region, and some fossil evidence supports this premise. Existing geological information puts modern Alcidae in the North Pacific as early as six million years ago, but also suggests an unknown ancestry extending over 40 million years before that time. While the suborder is uniform enough to include all of the auks in one family, there are still some very interesting differences between species, both in physical characteristics and in life patterns. Not surprisingly, there are also some discrepancies among experts in alcid taxonomy. As of 2002, ornithologists recognize 13 genera and 22 living species, with some experts condensing the number of genera to as few at 10.

Although there are no formal subfamilies, the living auks can be divided into eight lineages. The dovekie or little auk (Plautus alle, also known as Alle alle) is the sole member of the first group. The second group numbers three species: the razorbill (Alca torda), the common murre (Uria aalge), and the thick-billed murre (Uria lomvia). Three species of guillemots (Cepphus) form the third group, while the fourth and fifth are comprised of murrelets: Brachyramphus (two species) and Synthliboramphus (four species), respectively. The sixth group holds five species of auklet (genera Ptychoramphus, Cyclorrhynchus, and Aethia) while the seventh holds a single species, the rhinoceros auklet (Cerorhinca moncerata). Comprising the final group are three species of puffin (Fraturcula). The great auk (Pinguinus impennis), a flightless North Atlantic seabird and the only extinct member of the Alcidae, disappeared in 1844.

Physical characteristics

The auks are well-developed for their role as marine birds; so well, in fact, that they use land only for breeding. Living species range 6–18 in (12–45 cm) in length and weigh 0.17–2.4 lb (0.4–1.1 kg). (The extinct great auk [Pinguinus impennis] reached over 11 lb [5 kg].) The wings are relatively narrow and short, and the tail is short. The foretoes are webbed, with no toe on the back of the foot. The plumage is generally black, white, and gray, although the Brachyramphus murrelets develop brown summer plumage.

Many peculiarities distinguishing this family involve adaptations to diving and underwater "flight." These include dense, firm plumage; short, narrow wings; displacement of the feet toward the back, and consequently, a rather upright posture when standing on land; great development of the sternum, the coracoids, and the furcula; strongly developed breast muscles; large air sacs; a high blood hemoglobin content when compared to many land birds; and a high concentration of erythrocytes. While the alcids share many adaptations with their unrelated ecological counterparts in the Southern Hemisphere, the penguins (family Spheniscidae), the northern seabirds have almost all retained their flying abilities.

The larger species lose all their flight feathers at once in a molt shortly after the summer breeding season. The auks are then flightless for up to 45 days. Due to their small wings, most auks need a running, splashing start on the surface of the water to become airborne.

The bills of auks display a bewildering variety of forms and functions, unmatched by any other family and especially striking in such a small family. The razorbill was named because its long, sharp bill looks like an old–fashioned straight razor. The puffins have very deep bills that are laterally compressed. The dovekie has a very short, pointed bill that resembles that of a passerine. The guillemots have simple, straight bills. The parakeet auklet (Aethia psittacula) has the oddest-looking bill, with a lower half that turns up towards the tip—this feature apparently facilitates the capture of jellyfish.

Distribution

Exclusively in the Northern Hemisphere, throughout the Arctic, North Atlantic, and North Pacific.

Habitat

Alcids live almost exclusively on the surface of colder ocean waters, with breeding on shorelines, seaside cliffs, islands, and (in a few species) coastal forests.

Behavior

Their flight is fast and boisterous, although rather clumsy in appearance. The relatively small wings of most species require fast wingbeats, and most auks need some distance to become airborne. Auks are most often seen flying low over the surface of the ocean. Auks are superb swimmers and divers: studies using depth recorders attached to the birds have indicated that some species may reach depths of 600 ft (183 m). Under water, auks propel themselves with powerful beats of their half-open wings, while the legs are stretched back with the webbed feet functioning as a rudder.

Feeding ecology and diet

Auks draw their sustenance exclusively from the ocean. The larger species, such as murres, razorbills, guillemots, and puffins, prefer small fish that live in great numbers in the open ocean or on the ocean floor; they also feed, to a lesser degree, on small cephalopods, larger crustaceans, and other invertebrates. The smaller species, such as the dovekie, feed mainly on crustaceans, mollusks, chaetopods, and various other marine invertebrates. Many species fly well out over the ocean in search of food. Marbled murrelets (Brachyramphus marmoratus), which nest further from the water than other auks, will commonly fly 50 mi (80 km) from their nesting areas to forage.

Auks do not skim food from the surface of the water, nor do they dive into the sea directly from the air. Instead, they rest on the surface, then poke their heads under and tip forward, thrusting their bodies down and driving themselves forward with their wings as they swim in search of prey. This technique is called "pursuit diving."

Reproductive biology

All auks are monogamous, although pairs do not always stay together for life. Most species also show a strong inclination to return annually to the same nesting site.

Eight species of alcids copulate only at sea, a somewhat mysterious breeding strategy. Theories include avoidance of predators, avoidance of interfering males of their own species, and the possibility that females use this situation to select the more fit males.

Both sexes share in incubation and rearing of the young. Most species lay only one egg, the weight of which is roughly one tenth to one fifth that of the female. The newly hatched chicks, which are able to see, are covered with a dense downy coat. In a strategy unique to the Alcidae, young birds of several species leave the nest two to three weeks after hatching and venture out to live on the sea with their male parent until they become independent. The plumage of the juveniles resembles the winter plumage of the adults in color. Males and females have the same breeding plumage.

Conservation status

While the great auk is extinct, none of the extant species is considered Endangered. Several species, however, are classed as Vulnerable, with Xantus's murrelet (Synthliboramphus hypoleucus) and the marbled murrelet of particular concern. Xantus's murrelet, whose breeding grounds are restricted to the Baja peninsula and coastal islands off southern California, is threatened by introduced predators such as cats and rats as well as habitat degradation. The marbled murrelet population in the contiguous United States as of 1999 (perhaps 17,000 pairs) was estimated to be declining at about five percent per year due to habitat loss, and the U.S. Fish and Wildlife Service lists the species as Threatened. Human predation is no longer a critical threat to alcids, but oil spills and other ecological threats are cause for concern. Thousands of auks drown every year in fishing nets.

Significance to humans

The auks no longer support the kind of industry that flourished on the bodies of great auks, but significant hunting still takes place. Several species are hunted for subsistence in Greenland, Canada, and Alaska, and large hunts for two species are permitted in Newfoundland.

Species accounts

Resources

Fuller, E. The Great Auk. New York: Harry N. Abrams, 1999.

Gaston, A. J., and I. L. Jones. Bird Families of the World: The Auks (Alcidae). Oxford: Oxford University Press, 1998.

Elphick, Chris, John B. Dunning, Jr., and David Allen Sibley. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf, 2001.

DeSanto, Toni L., and S. Kim Nelson. "Comparative Reproductive Ecology of the Auks (Family Alcidae) with Emphasis on the Marbled Murrelet." USDA Forest Service General Technical Report 152 (1995): 33–47.

Friesen, V. L., A. J. Baker, and J. F. Piatt. "Phylogenetic Relationships Within the Alcidae (Chadriiformes: Aves) Inferred from Total Molecular Evidence." Molecular Biology and Evolution 13, 2 (1996): 359–367.

Hipfner, J. Mark. "Timing of Nest Departure in the Thick-billed Murre and Razorbill: Tests of Ydenberg's Model." Ecology 80 (1999): 587–596.

Hunter, F. M., and I. L. Jones. "The Frequency and Function of Aquatic Courtship and Copulation in Least, Crested, Whiskered, and Parakeet Auklets." The Condor. 101 (1999): 518–528.

IUCN–The World Conservation Union. "Alcidae." The 2000 IUCN Red List of Threatened Species.

[Article by: Matthew A. Bille; Cherie McCollough]