Mystery Bird: Green-winged Teal, Anas crecca

Green-winged. Teal (female) - bill shape seem right for the species. I would expect a female Blue-winged Teal to have a larger bill and a pale patch at the base of the bill.

I think you are correct Michael, a female Green-winged Teal, Anas carolinensis: dark grey bill; pale brown head and neck; dark brown cap and eye line; dark brown back and upperwing coverts scalloped with buff- the smaller bill and lack of white at the base of the bill eliminate both the Blue-winged and Cinnamon Teals.

Taxonomically many sources still list the Green-winged Teal as a subspecies of the Common Teal- Anas crecca carolinensis, and the AOU is currently reviewing it's own classification with research showing that A. carolinensis was more closely related to A. flavirostris (Speckled Teal) than either was to Old World A. crecca, but both the IUCN and Birdlife International agree with it's designation as a separate species as noted above (and even the Blue-winged Teal is now no longer considered really a teal but a shoveler that should be moved to the genus Spatula).

Again, an additional field mark to note -- the upper part of the undertail coverts is unmarked buff -- in males this would be outlined in black. Other small ducks don't show this mark.