Scaup are a long-standing ID problem, but with time spent looking at them, the Greaters can be picked out. Most of the time, it is a matter of picking the Greaters out of the majority of Lessers. At some places, in particular around Pace Point and Paris Landing, Greaters can be found in some numbers, sometimes in solid flocks.
Following are several ID points, but sometimes distant scaup are best as Scaup sp.