This female is showing practically none of the head pattern that is typically looked for on female Scoters. She did have a slightly paler area on the lores, but this is lost in this photo. Luckily, the white secondaries are hard to miss, and the overall darkness says nothing but Scoter. You can also see the shape of the feathering at the base of the bill, as it runs well out onto the bill. This is very different on the other two Scoters.