I wound up spending 5 hours on Randall's Island today. I'm too wiped out to sort through photos just yet. There are still Snow Buntings on the northeast shore; I saw the Horned Lark again in the southeast near the Triboro Bridge; and there was a Common Loon off the southwest shore, a hundred yards or so south of the Ward's Island Bridge. From the road 20 yards away, I noticed a large bird very close to shore, thought "isn't that a loon?", got my glasses on it, noted the huge bill and the transitional plumage (dull winter head, but the back starting to look like the breeding "checkerboard" pattern), and then it dove--and as far as I saw, never came up. I think it must have surfaced north of the bridge.
Anyway, Common Loon! My 69th species in New York county this year.