What is "patchhead"

Scoter \Sco"ter\, n. [Cf. Prov. E. scote to plow up.] (Zo["o]l.) Any one of several species of northern sea ducks of the genus Oidemia.

Note: The European scoters are Oidemia nigra, called also black duck, black diver, surf duck; and the velvet, or double, scoter ( O. fusca). The common American species are the velvet, or white-winged, scoter ( O. Deglandi), called also velvet duck, white-wing, bull coot, white-winged coot; the black scoter ( O. Americana), called also black coot, butterbill, coppernose; and the surf scoter, or surf duck ( O. perspicillata), called also baldpate, skunkhead, horsehead, patchhead, pishaug, and spectacled coot. These birds are collectively called also coots. The females and young are called gray coots, and brown coots.