[Mystery birds] Green-winged Teal, Anas carolinensis, photographed at San Bernard Refuge, Texas. [I will identify this bird for you tomorrow]
Image: Joseph Kennedy, 8 April 2009 [larger view].
Nikon D200, Kowa 883 telescope with tsn-pz camera eyepiece 1/350s f/8.0 at 1000.0mm iso400.
Please name at least one field mark that supports your identification.
I can't see the toes to know whether they're webbed or not, but everything about this bird -- its horizontal posture, its complexly marked body plumage, its large head, and the contrasting colorful panel on the secondaries -- says "puddle duck." It's also obviously a small, even a tiny, puddle duck, if the cattail leaves are anything to go by.
Starting at the rear, we find a tail that is neither especially long nor especially pointed; that lets us rule out wigeon, for example. The lateral undertail coverts are plain white, forming a contrasting patch just below the outer tail feathers; this is the "shadow" of a male Green-winged Teal's creamy fender, and is enough to put us on the right track.
The belly is relatively unmarked and contrasts strongly with the heavily marked breast; none of the "blue-winged" ducks shows that white oval from beneath. Cinnamon and Blue-winged Teal also have brighter feet than this, with a noticeable orange tinge lacking on the gray tarsus of our quiz bird.
The speculum -- that colorful patch on the secondaries -- just peeks out from beneath the tertials and the greater coverts. It appears to be dark blue, but it's worth remembering that iridescent colors vary depending on angle and lighting, and that like a hummingbird's gorget, a single duck's speculum can seem to range from black to purple to blue to green in the space of just a few moments.
Finally, let's look at this bird's head. Bill shape and length aren't going to be very helpful, but the steep, full nape and flat crown give our mystery duck an impressively large and square head, typical of Green-winged Teal and quite unlike the long, rounded contours of a Blue-winged or Cinnamon Teal. The strong black lines crossing the face are also characteristic of Green-winged Teal.
We can assume that a Green-winged Teal photographed in Texas is, in fact, a Green-winged Teal carolinensis and not a Common Teal crecca or nimia, Old World birds that occur regularly (and probably more frequently than they are detected) on both coasts and in the inland west. Female-plumaged birds show small but critical differences in the wing pattern. Unfortunately, unless this photo spreads its wings, we'll never now.
Female Blue-Winged Teal (Anas discors)
Blue-winged Teal because of the flash of blue on the wing, and the general speckled featehr pattern and female becuase it lacks the distinctie strip on the head that the male has.
I'll go with female Green-winged Teal - I'm not seeing the blue on the fore-wing I would expect in the other two teals.
The pale breast and the lack of a pale patch at the base of the bill also fits Green-winged Teal.
Another vote for green-wing teal. And I'll point out the grayish leg color.