What is "red-headed duck"

Redhead \Red"head`\ (-h?d`), n.

1. A person having red hair.

2. (Zo["o]l.)

   1. An American duck ( Aythya Americana) highly esteemed as a game bird. It is closely allied to the canvasback, but is smaller and its head brighter red. Called also red-headed duck. American poachard, grayback, and fall duck. See Illust. under Poachard.

   2. The red-headed woodpecker. See Woodpecker.

3. (Bot.) A kind of milkweed ( Asclepias Curassavica) with red flowers. It is used in medicine.