THE GENUS LAIIUS. 
251 
time, to pick up the larvae and worms exposed by the 
plough. 
Breeding. — Nothing is known with precision in regard 
to the period of incubation. Their nests are composed of 
dried grass, arranged in a slovenly manner, and deposited 
in a superficial cavity in the turf, or not unfrequently on 
the bare rock. The number of eggs is generally three. 
The young are at first covered with a very fine thick down : 
they leave the nest very soon after exclusion, and secrete 
themselves in crevices, or behind stones ; but they do not 
take to the water till they are fully fledged. The young 
birds are mottled with dull-grey, and brownish ; the beak 
and feet, as well as the iris, are at first dark, and become 
lighter as the bird advances in age : the full and perma- 
nent plumage is not acquired in general till the third year. 
After this, at the autumnal moulting, the head and neck 
in many become streaked with pale brown lines, which dis- 
appear in spring. 
Country, — This genus is not confined to any particular 
portion of either the Old or New Continent, being found 
everywhere, along the shores, from the frozen regions of 
the North to those of the South Pole, and appearing equally 
in the Torrid Zone. Their partial and general migrations 
have not been sufiiciently explained. 
Uses. — In the economy of Nature, one of the principal 
uses of these birds may be to clear the coast of animal re- 
mains, which would otherwise produce a noxious effect by 
putrefaction ; in the same manner as the vultures, crows, 
and eagles, perform this office in the interior of the conti- 
nents and islands. This may in some degree explain their 
general diffusion. With regard to man, they do not seem 
