AUKS. 411 



are very active, keeping their head and body continually in 

 motion, and frequently expanding their tail and wings. 



The type of this sub-family is — 



The Senegal Fin-foot {Hcliomis Senegaknsis) 



FAMILY III. 



THE AUKS. ALCID/E. 



General Characteristics. — Bill more or less long, generally compressed on the 

 sides, and the culmen usually curved to the tip, which is sometimes hooked ; the 

 wings generally short, and more or less imperfectly formed ; the tad short and gra- 

 duated ; the tarsi usually short and compressed ; the toes entirely webbed, with the 

 hind toe small or wanting. 



The birds belonging to this family are distinguished by having 

 only three palmated toes, and where a fourth or hind toe does 

 exist, it is very small, without any web, and inclined forwards. 

 The Alcidse are distributed in most parts of the world, but most 

 numerously in high northern and southern latitudes. They are 

 found upon the barren rocky shores of the Arctic and Antarctic 

 lands and islands, often in flocks consisting of vast numbers of 

 individuals. They pass the greater part of their time in the sea, 

 whence they obtain an abundant supply of food, which they pro- 

 cure by diving. In these birds, shortness of wing, and consequent 

 deficiency in their powers of flight, are carried to the greatest 

 extreme, the wings of the penguins and other allied genera being 

 so small and imperfectly developed as to be totally unfit for flying, 

 and adapted to act merely as fins to aid their progress beneath 

 the water. As in the Colymbidce, the legs of these birds are 

 placed far backwards, but at scarcely so great an angle with the 

 body. In consequence of this, they are enabled to sit in an upright 

 attitude, resting equally on the foot and on the whole length of 

 the tarsus. They are all birds of the ocean, never resorting to 

 fresh water, as the divers do. Many of the species that are able 

 to fly, nestle on the rocks and precipices, where they lay a single 

 egg of conical form, a shape which prevents it from rolling away, 

 or moving except within a circle of the diameter of its own length, 

 on the bare ledge of rock where it is deposited. Some burrow in 

 the light sandy soils of the small islands they frequent, and the 

 penguins, and other species that have not any power of flight. 



