Last Sunday I posted photos of diving ducks. Here is the ID. In each case I had the advantage of having watched, and photographed, the bird swimming on the surface and then diving. If I found these photos without the context, I would have been hesitant about putting a name on them.
Diver #1 - Red-breasted Merganser
Diver #2 - White-winged Scoter - I am not sure it was fair including this one since the white-wing was not at all visible, but then it is not visible in the companion photograph below which is a good thing to know when looking at black ducks. It took me a lot of searching to discover finally that the Surf Scoter also has red legs, but not the Black Scoter. If anyone knows how to distinguish White-winged & Surf in the diving photo, I would love to hear from you. I had the distinct advantage of watching the lone White-winged Scoter, so IDing the photo was not a problem
Diver #3 - Common Eider
Diver #4 - White-winged Scoter