Surf Scoter, Melanitta perspicillata
Surf Scoters are sea ducks; the males are unmistakeable, black plumage with white forehead and nape, and the spectacular large, irregularly-shaped, and multi-colored bill. A few of these ducks winter every year on salt-water Shoreline Lake alongside southern San Francisco Bay in Mountain View, and that's where I've taken most of these pictures. Otherwise, scoters, especially the less common species, Black and White-winged, are difficult to photograph (I don't have any), as they mostly are seen in the ocean just beyond the surf line.
Two white patches on the side of the face, the front one relatively faint, indicate an adult female rather than a juvenile; compare the juvenile further down the page with the bright forward patch.
This first-winter bird can be identified as a male by the yellow just beginning to appear on the bill, which is larger and less regularly shaped than the female bill; compare the female adults further up the page and the first-cycle female just below.
First-winter female; note the bill smaller than the first-winter male further up the page.
Males competing for the attention of the female during the fall "pairing-up" season, prior to the breeding season which begins in early spring.
A surf scoter out of the water -- a rare sight indeed.