Lesser Scaup
Aythya affinis

f7.1 @ 1/5000s, ISO:2000, Nikon D3S w 500mm and 1.7X teleconverter

"Lesser Scaup," Wikipedia, the free encyclopedia. Adult females (hens) have a white band at the base of the bill, often a lighter ear region, and are otherwise dark brown all over, shading to white on the mid-belly.
Little Pond, Falmouth, Massachusetts