Several people answered Tuesday's teaser correctly — the two Green-winged Teal on the left are American Green-winged Teal, and the one with the racing stripe on the right is the Eurasian or Common Green-winged Teal, not common around here at all.
Congrats to all.
The Euro Teal was the only one I could guess: I remember seeing the Euro during the MC/BCA walk a couple of weeks ago, and the “racing stripe” was distinctive.