Alcidae
| Auks Temporal range: Late Eocene – Recent 35–0 Ma |
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| Parakeet auklets (Aethia psittacula) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Clade: | Pan-Alcidae |
| Family: |
Alcidae Leach, 1820 |
| Type species | |
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Alca torda Linnaeus, 1758 |
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| Subfamilies | |
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An auk or alcid is a bird of the family Alcidae in the order Charadriiformes. The alcid family includes the murres, guillemots, auklets, puffins, and murrelets.
Apart from the extinct great auk, all auks are notable for their ability to "fly" under water as well as in the air. Although they are excellent swimmers and divers, their walking appears clumsy.
Several species have different common names in Europe and North America. The guillemots of Europe are referred to as murres in North America, if they occur in both continents, and the little auk is referred to as the dovekie.
Auks are superficially similar to penguins having black-and-white colours, upright posture and some of their habits. Nevertheless, they are not closely related to penguins, but rather are believed to be an example of moderate convergent evolution. Auks are monomorphic (males and females are similar in appearance).
Extant auks range in size from the least auklet, at 85 g (3 oz) and 15 cm (5.9 in), to the thick-billed murre, at 1 kg (2.2 lb) and 45 cm (18 in). Due to their short wings, auks have to flap their wings very quickly in order to fly.
Although not to the extent of penguins, auks have largely sacrificed flight, and also mobility on land, in exchange for swimming ability; their wings are a compromise between the best possible design for diving and the bare minimum needed for flying. This varies by subfamily, the Uria guillemots (including the razorbill) and murrelets being the most efficient under the water, whereas the puffins and auklets are better adapted for flying and walking.
The feeding behaviour of auks is often compared to that of penguins; both groups are wing-propelled pursuit divers. In the region where auks live, their only seabird competition is the cormorants (which are dive-powered by their strong feet). In areas where the two groups feed on the same prey, the auks tend to feed further offshore. Strong-swimming murres hunt faster schooling fish, whereas auklets take slower moving krill. Time depth recorders on auks have shown that they can dive as deep as 100 m in the case of Uria guillemots, 40 m for the Cepphus guillemots and 30 m for the auklets.
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Wikipedia