mallard

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A wild duck (Anas platyrhynchos) of which the male has a green head and neck. Most domestic ducks descend from the mallard.

Century Dictionary and Cyclopedia

1. n. The wild drake; the male of the common wild duck.
2. n. Hence The common wild duck, Anas boscas, the feral stock whence the domestic duck in all its varieties has descended, and the typical representative of the family Anatidœ and subfamily Anatinœ. See duck. The mallard is from 22 to 24 inches long, by 32 to 36 in extent of wings. The male has the head and neck glossy-green, succeeded by a white ring; the breast purplish-chestnut; the lower back, rump, and tail-coverts glossy-black; the tail-feathers mostly whitish, with a curly tuft; the wing-speculum iridescent, bordered with black and white; the bill greenish-yellow; the feet orange-red; and the iris brown. The female has the wings and feet as in the male, the bill greenish-black blotched with orange, and the body-colors variegated in fine pattern with lighter and darker brownish shades. The mallard is found in nearly all parts of the world. It nests on the ground, laying usually from 8 to 10 yellowish-drab eggs measuring about 2¼ by 1⅗ inches.

Wiktionary

1. n. A common and widespread dabbling duck, Anas platyrhynchos, whose male has a distinctive dark green head.

GNU Webster's 1913

1. n. (Zoöl.) A drake; the male of Anas boschas.
2. n. (Zoöl.) A large wild duck (Anas boschas) inhabiting both America and Europe. The domestic duck has descended from this species. Called also greenhead.

WordNet 3.0

1. n. wild dabbling duck from which domestic ducks are descended; widely distributed