Joseph, what did you think? Did you see him move his head?
We have lots and lots of both species of scaup here, and Ring-necked Ducks are common. They hybridize in the books, but I have not seen a hybrid here. Can't speak for California, though.
Tom, hybrid Tufties x Pochards don't commonly show up in California! That would be some rare duck!
...And I'll have to surrender Tuftie on the shape of the head. I thought the photo might have fooled me on that, but I suppose not. Anyway, you folks would know!
However, Joern, I'm surprised you add in the tuft itself as a criteria in the photo. Scarce as Tufties are here, I've often seen perfect males, in positions like this one, showing not a trace of their tuft--even though in fact it was a nice long one.
Maybe North Pacific Tufties use more gel?
Guess I'll have to reluctantly buy into the scaup x Ring-necked Duck. Greater Scaup, then; that's a lot of white; and he sure didn't get it from the Ring-necked side of the family. Hm. Could be back-bred too. I'm not sure that I agree about the bill being essential: if it were a scaup bill, you'd be about where we are now; if it were a Ring-necked bill you'd be about where we are now. I suppose that's why I really didn't want to go for that domed head. I was trying to angle it from the camera in such a way that it wasn't domed. Oh well....
But tell us what you think, Joseph. We'd like to hear your California take on things.