We had hoped for a Black at TVA Lake, but found this one at Robco instead.

This female-type Black was picked out of a large number of Scaup on Robco. This bird initially associated with a pair of Lesser Scaup, them made it's way into the big raft, where it was tough to pick up.

This is a distant photo, but shows what you see when scanning divers a long way off. The dark body and cap contrast well to the pale cheek and throat. These birds can be overlooked easily, as the overall pattern is quite similar to a winter male Ruddy Duck.