Auk
Auks are Northern Hemisphere seabirds that swim and dive like penguins.
Auks, or alcids, belong to the family Alcidae within the order Charadriiformes, a group that also includes plovers, gulls, and skuas. The family comprises 25 species (extant or recently extinct) across 11 genera, encompassing murres, guillemots, auklets, puffins, and murrelets. They are distributed exclusively throughout the Northern Hemisphere. With the sole exception of the extinct great auk, all living auks are capable of flight, though their short wings require rapid flapping. They are exceptional swimmers and divers, propelling themselves underwater with their wings in a manner that resembles flying, but their walking on land is notably awkward. Auks bear a superficial resemblance to penguins, sharing black-and-white plumage, an upright stance, and certain habits; however, this similarity is a result of convergent evolution, as the two groups are not closely related. Males and females are monomorphic, appearing alike. The name "auk" derives from the Old Norse *ālka*, via Icelandic and Norwegian terms, while the family name Alcidae originates from the genus *Alca*, coined by Carl Linnaeus in 1758 for the razorbill, itself from the Norwegian *alke*. Auks exhibit a trade-off in their wing design, optimized for underwater propulsion but only minimally adequate for flight. This varies by subgroup: murres and some murrelets are most efficient underwater, while puffins and auklets are better adapted for flying and walking. As wing-propelled pursuit divers, they compete with cormorants, but tend to feed further offshore. Murres hunt fast schooling fish, whereas auklets target slower krill, with diving depths recorded up to substantial ranges for different genera. Auks are pelagic, spending most of their lives at sea and coming ashore only to breed. They are monogamous, often forming lifelong pairs, and typically lay a single egg per year, reusing the same nesting site. Nesting habits vary: some species form large colonies on cliff edges, others breed in small groups on rocky coasts, and puffins, auklets, and some murrelets nest in burrows. Most species are colonial, except for certain murrelets.
- Extant species
- 22–24
Lore & Background
Auks are superficially similar to penguins, with black-and-white colours, upright posture, and some habits, but they are not closely related; this is considered moderate convergent evolution. They are monomorphic, with males and females similar in appearance. Extant auks range from the least auklet at 85 g and 15 cm to the thick-billed murre at 1 kg and 45 cm. Due to their short wings, auks flap very quickly to fly, and their wings are a compromise between diving efficiency and the minimum needed for flight. The Uria guillemots and murrelets are most efficient underwater, while puffins and auklets are better adapted for flying and walking.
Reader's Guide
Auks are significant as a seabird family that exemplifies convergent evolution with penguins, yet they retain flight and occupy a distinct ecological niche in cooler northern waters. Their feeding behaviour as wing-propelled pursuit divers is compared to penguins, and they compete with cormorants in their range. Auks are pelagic, spending most of their lives at sea and going ashore only to breed. They are monogamous, typically lay a single egg, and use nesting sites year after year. Some species nest in large colonies on cliffs, others in small groups on rocky coasts, and puffins, auklets, and some murrelets nest in burrows. Historically, auks were considered an early charadriiform lineage, but genetic analyses show their peculiarities result from strong natural selection from a wading shorebird ancestor. Their closest living relatives appear to be skuas, with separation about 30 million years ago. The earliest unequivocal fossils are from the late Eocene, about 35 million years ago. Most extant genera are known from the late Miocene or early Pliocene, about 5 million years ago. The family's limited geographic range and glacial cycles have shaped its diversity, with more species in the Pacific than the Atlantic.
Did You Know?
- The word 'auk' is derived from Icelandic álka and Norwegian alka or alke, from Old Norse ālka.
- Auks are monomorphic, meaning males and females are similar in appearance.
- The thick-billed murre can weigh up to 1 kg and reach 45 cm in length.
- The flightless subfamily Mancallinae, sometimes included in Alcidae, had fossils found only on the Pacific Coast of southern North America, and became extinct.
Frequently Asked Questions
What is an auk?
Auks are a family of Northern Hemisphere seabirds (Alcidae) within the order Charadriiformes, making them relatives of gulls and terns rather than penguins. The group encompasses familiar species such as puffins, murres, auklets, and murrelets.
Can auks fly?
Yes—every living auk species is a capable flier, even though their short, rigid wings make them look clumsy on land. Their true talent is underwater, where they power through the water as efficient swimmers and deep divers.
How many species of auk are there?
Taxonomists currently recognize roughly 22 to 24 extant species distributed across 11 genera. The exact count shifts slightly depending on whether certain lineages are treated as separate species or subspecies.
What is the great auk?
The great auk (Pinguinus impennis) was a large, flightless auk that went extinct in the 1840s after centuries of human hunting. It is the only auk that ever lost the power of flight, which is why people often mistake it for a penguin.
Why do auks look so similar to penguins?
The resemblance is a product of convergent evolution: both groups independently evolved streamlined bodies and flipper-like wings for efficient underwater hunting. Unlike penguins, however, auks are restricted to the Northern Hemisphere and, apart from the extinct great auk, all retain the ability to fly.
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