An auk is a bird in the family Alcidae. The most notable species in this family may be the Great Auk, a giant bird that lived in the North Atlantic until the 1800s, when it was hunted to extinction. These birds achieved a height of 33 inches (85 centimeters) and much like the dodo, another famous extinct bird, they were poorly adapted to aggressive predation by humans. Surviving auks are significantly smaller.
The auks include razorbills, auklets, puffins, guillemots, and murres. Physically, auks resemble penguins. They are stockily built and they have distinctive black and white plumage. Despite the resemblance, auks are more closely related to gulls than penguins. The superficial resemblance to penguins is an example of convergent evolution, where unrelated species develop similar traits. These traits are adaptive responses to various native environments.
Auks are excellent swimmers and divers, using their muscular wings to propel themselves through the water in search of prey. All auks can fly, although some species are more adept than others, and the birds tend to look awkward on land, as they have not adapted to walk gracefully. The birds prefer open water in northern regions of the world where they can readily hunt for prey species. Cold water provides the best hunting environment for these birds, and they may take advantage of cold upwellings to access ample sources of prey.
Habits vary among auk species. While the birds spend much of their time on the open water, they nest on shore and some species will invest energy in defending a nest on land when they are not actively nesting. Auks are vulnerable to habitat pressures like warming seawater because they have adapted to live in a very specific climate with very particular ocean conditions. Fossil evidence shows that auks were once much more diverse and widely distributed, illustrating the way that populations changed as the Earth's climate shifted over the course of geologic history.
Some zoological parks and conservation programs maintain auk populations in captivity. Visitors can see and sometimes interact with the birds up close and the colony may include other seabirds to create a more natural feeling environment, especially in facilities that educate members of the public about conservation issues. Researchers who study auks and the species that live with them can take advantage of captive auk populations for some of their work, in addition to observing populations in the wild.