I stopped at Hain's Point this morning in a desperate attempt to find
Canvasback and White-winged Scoter before the end of year.  I failed on
both accounts, but did find the following:

1004 LESSER SCAUP (this is a fairly accurate count as I actually did
count them one-by-one)
1 female LONG-TAILED DUCK (in with the scaup)
1 female COMMON GOLDENEYE (near the airport)
4 BUFFLEHEAD
1 COMMON LOON (Tidal Basin)
4 HORNED GREBE
4 PIED-BILLED GREBE
1000 CANADA GOOSE (this is a very rough guess because, well, they're
Canada Geese ;-)
20 MALLARD (incl. the usual Hain's Pt oddballs)

The most interesting thing about the scaup is that they are 99.9% males.
 I only saw 1 female in the whole flock.  And I think they are young
males since they seem to have a fair amount of markings on the flanks.

I couldn't find any Cackling Geese, but think that there are at least 2
subspecies of Canadas in these flocks, including a smaller one than the
usual B. c. canadensis (I think they're B. c. interior).

Good birding (and please let me know if you see a Canvasback or
White-winged Scoter in DC between now and the end of the year),
Paul Pisano
Arlington, VA