Great Auk - Description

Description

Standing about 75 to 85 centimetres (30 to 33 in) tall and weighing around 5 kilograms (11 lb) as adult birds, the flightless Great Auk was the largest of both its family and the order Charadriiformes. The auks that lived further north averaged larger in size than the more southerly members of the species. Males and females were similar in plumage, although there is evidence for differences in size, particularly in the bill and femur length. The back was primarily a glossy black, while the stomach was white. The neck and legs were short, and the head and wings small. The auk appeared chubby due to a thick layer of fat necessary for warmth. During summer, the Great Auk developed a wide white eye patch over the eye, which had a hazel or chestnut iris. During winter the auk molted and lost this eye patch, which was replaced with a wide white band and a gray line of feathers which stretched from the eye to the ear. During the summer, the auk's chin and throat were blackish-brown, while the inside of the mouth was yellow. During the winter, the throat became white. Some individuals had grey plumage on their flanks, but the purpose of this is unknown. The bill was large at 11 centimetres (4.3 in) long and curved downwards at the top; the bill also had deep white grooves in both the upper and lower mandibles, up to seven on the upper mandible and twelve on the lower mandible in summer, though there were fewer in winter. The wings were only 15 centimetres (5.9 in) in length and the longest wing feathers were only 10 centimetres (3.9 in) long. Its feet and short claws were black while the webbed skin between the toes was brownish black. The legs were far back on the bird's body, which gave it powerful swimming and diving abilities.

Hatchlings were gray and downy, but their exact appearance is unknown, since no skins exist today. Juvenile birds had less prominent grooves in their beaks and had mottled white and black necks, while the eye spot found in adults was not present; instead, a gray line ran through the eyes (which still had the white eye ring) to just below the ears.

The auk's calls included low croaking and a hoarse scream. A captive auk was observed making a gurgling noise when anxious. It is not known what its other vocalizations were like, but it is believed that they were similar to those of the Razorbill, only louder and deeper.