Monday, March 1, 2010
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Answer by Tony Leukering
As most respondents noted, this week's quiz bird is a duck. Many also noted that as the bird is grazing on lawn, we might begin our search for an ID with just a trio of possibilities: the two ABA-area wigeon species and Mallard, as these are the inveterate grass-eaters among dabbling ducks. Note that I didn't even consider the diving ducks, as they don't graze grass on land (at least, not at all regularly) and they generally lack fringed body feathers as shown on our bird's rump.
At this point, I will borrow parts of Margie Joy's answer, but I will return to further discuss the points she raises and the ones she doesn't.
"This is a photo of the tail end of a duck that seems to be grazing on grass. This behavior, together with whitish belly and rust-colored sides, points me to wigeon. But there are two ABA-area wigeons to consider, American and Eurasian, and they are frustratingly similar.
"In my field guides, the most-often mentioned ways to distinguish the two species have to do with head/body coloring on adult males in basic ("breeding") plumage. No help there, as I cannot see this bird's head. It's not an adult male, as it doesn't show the black undertail coverts that mark such birds of both species. Underwing color/pattern is another commonly-shown identifying mark, but these don't show in the quiz photo, so no help there either.
"I was going to give this up as unidentifiable (by me, anyway) when I found an online article on The identification, molts, and aging of American and Eurasian Wigeons in female-type plumages, by Cox and Barry in Birding (March/April 2005). This article states: The pattern of the secondary upperwing coverts is the most reliable characteristic for both aging and identifying wigeons, and illustrates the point quite clearly. I had a hard time sorting out feather groups because of the foreshortened angle of the photo and the posture of the duck (as well as my own shaky knowledge of feather groups), but one thing seems pretty obvious -- the quiz bird shows very pale feathers above the dark secondaries. These feathers don't seem to form a single row of completely white feathers (adult female American Wigeon) but more a straight-edged patch of very pale gray feathers with white edges (first-cycle male American Wigeon). So, based on my interpretation of what I read in this article, my best guess is American Wigeon."
Thanks, Margie. Though a large majority of respondents got the quiz correct, I wonder what would have happened had I had an identical picture of a Eurasian Wigeon, as American is obviously the default wigeon in the ABA area.
Quite a few respondents noted consulting Cameron and Jessie's paper on wigeon in that 2005 issue of Birding and all those that did noted the paper's discussion about the greater coverts. I find it interesting that only one picked up on the single mark that I was highlighting with this quiz photo, though it wasn't used to identify the bird to species. First, of all respondents that noted Cox and Barry's comments about the usefulness of the greater coverts in ageing and sexing wigeon, they were, to a person, confused by the quiz bird. All of them got it right, but, again, I wonder what would have happened if I had presented a Eurasian Wigeon.
The point that I wished to make about wigeon ID in this week's quiz is illustrated with an arrow in the picture below: the innermost secondary (the one immediately distal to the three tertials).
As many of us know, American Wigeons have white axillars, while Eurasians have gray ones and this feature can assist us in identifying flying wigeon seen from below. When dealing with the innermost secondary, we need to remember that the color difference of the axillars is reversed for this feather: white (or pale gray) in Eurasian, (darker) gray in American. The feather can be tricky to use unless one can accurately assess any lighting impacts, but given our straight-on view and with direct comparison to the very real whiteness of the tips of the greater coverts, we can be sure that our bird's innermost secondary is certainly not white and not even pale gray. Thus, our bird is an American Wigeon. Oh, it certainly might be a hybrid, but the combination of innermost secondary color and greater coverts color/pattern seems to suggest that our bird is a "good" American Wigeon. Finally, the picture was taken in February on the same date -- 6th -- and in the same place -- Seattle, King Co., WA -- as I photographed the hybrid gull presented in #335! In February, we can be certain that the bird is not a male, as any male wigeon in the ABA area in February ought to look like one -- like the bird pictured below photographed just minutes before I photographed the quiz bird. In this picture, we can see that the innermost secondary is useful in the ID of flying birds, too.
Incorrect species provided as answers:
Mallard - 1
American Robin - 1
Eurasian Wigeon - 1
Congratulations to the 21 of 24 getting the quiz correct:
Answer: American Wigeon