SUB-FAMILY MERGANINÆ
91. Mergus (Smew, Merganser, Goosander). Bill straight, slender, narrow, approaching to cylindrical; upper mandible hooked; edges of both mandibles armed with sharp teeth directed backwards; legs short, placed far backward.
ORDER COLUMBÆ
(Pigeons and Doves)
Bill swollen at tip, convex; the upper mandible covered at the base with a soft membrane in which lie the nostrils, with a valve over them; tarsi covered fore and rear with hexagonal scales.
The birds of this order have considerable powers of flight, and perch freely on trees or rocks. Their food consists principally of grain, seeds, and the leaves of herbaceous plants. The young are fed on a milky fluid secreted in the crop of the old birds.
FAMILY COLUMBIDÆ
Tail with twelve feathers; hind toe with the skin prominently expanded on the sides.