546 WEB-FOOTED BIRDS. 



AUKS. (Alca, Linn.) 



The BILL robust and shorter than the head, compressed, broad at 

 the base, higher in the middle, feathered to the nostrils, tumid, 

 grooved and plaited on the sides, hooked at the point; upper mandi- 

 ble convex, strongly curved from the middle, hooked and acute at 

 the tip ; the lower gibbous below the point, shorter and obliquely 

 truncated; the feathers of the face adv^ancing to the middle of both 

 mandibles. Nostrils medial, marginal, short, linear, pervious, half 

 closed by the feathered membrane, and scarcely perceptible. Tongue 

 thick, oblong and acute. Head depressed, narrowed before, and 

 rounded behind. Tibia much retracted ; tarsus rather robust, carin- 

 ated on both sides ; webs entire ; nails moderately curved, acute, 

 the middle one largest. Wings short, and acute ; quills sharp pointed ; 

 1st primary longest ; secondaries very short. The tail composed of 

 12 or 16 acute feathers. 



The sexes similar in their plumage. The young have smaller and 

 nearly even bills. They moult twice in the year, changing the co- 

 lors of the head. The feathers short. 



The true Auks live out at sea, not far from the shore ; those that 

 have the ability, fly rapidly, though usually but for short distances, 

 and generally dive the instant they alight ; they are very dexterous 

 beneath the water, pursuing their prey with great certainty and 

 address, making use of their wings as powerful oars. Though they 

 walk awkwardly, they yet sometimes proceed swiftly. They breed 

 in large companies in caves and clefts of rocks, where they also 

 retire for shelter and repose. They lay but a single disproportionately 

 large egg ; and the young are fed by regurgitation for a considerable 

 time, and also after leaving the eyry. They feed on fishes and small 

 marine animals, which they obtain chiefly by diving. 



These are chiefly arctic birds : the genus comprehends two widely 

 different and apparently incongruous species ; one of which, the 

 largest of the natural order to which it belongs, scarcely ever leaves 

 the arctic circle. 



