Auks are seabirds primarily found in the Northern Hemisphere’s cold oceans. These birds are highly adapted to marine life, spending most of their time at sea and only returning to land for breeding. They thrive in harsh environments.
Defining Characteristics of Auks
Auks belong to the family Alcidae within the order Charadriiformes. They have a compact, chunky body, with sizes ranging from small species like the least auklet (around 15 cm long and 85 g) to larger ones such as the thick-billed murre (up to 45 cm long and 1 kg). Auks generally display black or dark gray plumage on their upperparts and white underparts, which provides camouflage in the marine environment.
Auks have short, narrow wings, highly effective for “flying” underwater. These adaptations for diving mean their flight in the air requires rapid wing beats, and their movement on land can appear clumsy due to their legs being set far back on their bodies. Their webbed feet aid in swimming and maneuvering underwater. While superficially similar to penguins with their upright posture and black-and-white coloring, auks are not closely related; their resemblances are a result of convergent evolution.
Life in the Ocean
Auks are pelagic birds, spending most of their lives in the open sea and coming ashore primarily for breeding. They are found in cooler northern waters, including Arctic, subarctic, and temperate regions, with the highest diversity of species in the Pacific Ocean. They obtain food through pursuit diving.
Their diet primarily consists of small fish, crustaceans, and zooplankton. Species like murres and razorbills catch schooling fish such as sand eels, capelin, and herring, often diving to depths of 30-60 meters, with some recorded dives up to 180 meters. Smaller species, like the little auk, feed more on krill and copepods, sometimes filtering them from the water. Auks form large, dense breeding colonies on coastal cliffs and islands, where they typically lay a single egg, though guillemots can lay two. Both parents share incubation duties and care for their young.
Diversity of Auks
The family Alcidae encompasses 25 extant species across 11 genera. Puffins, such as the Atlantic Puffin, have a stocky build, black and white plumage, and large, brightly colored bills during the breeding season. They often nest in burrows in the soil on coastal cliffs or offshore islands.
Murres, like the common murre, are large auks with sleek black and white bodies and long, thin bills. They breed in dense colonies on bare rock ledges of cliffs, where their pear-shaped eggs are less likely to roll off. Guillemots, including the black guillemot, are typically chocolate-brown or black above and white below, with some displaying distinctive white wing patches or red legs. They also nest on rocky coasts and cliffs. The razorbill, the only living species in the genus Alca, has a black back, white belly, and a thick, laterally compressed black bill with a thin white line. They nest in crevices among cliffs and boulders.