Generally, the darker coloration of Scoters in flocks of other ducks stands out, but in this photo the female Scaup appear about as dark overall as the sleeping female Surf Scoter. Notice the white spot on the cheek of the sleeping Scoter. The most obvious difference in this photo between the Scoter and sleeping Lesser Scaup is the shape of the head. Notice the flat profile of the Scoter versus the obvious peak of all the Scaup.