Monday, January 9, 2012

Quiz #432 (2012-1-02) Solution

Click on picture(s) for a larger view.

Solution by Tony Leukering

In this week's quiz picture, we can see parts of seven birds, all obviously or assumingly ducks. The bird whose body just extends down into the top-left of the image is identifiable as a scoter, but nothing in this view allows specific ID. Enough of the heads of only three of the birds is visible to use that feature as an identification point, and all three of those are adult male Black Scoters, with their bills sporting large orange basal knobs. [Recall that the Old World form is now considered by the A.O.U. to be a separate species, Common Scoter, and that it can be identified in adult males by its knob being smaller and black and with a yellow saddle to the maxilla.] The leftmost bird , if a scoter, is a juvenile, as discerned by the whitish belly patch, which all juvenile scoters sport, but which is generally not seen on swimming birds (due to placement). Despite the illustrations in The Sibley Guide that show juvenile White-winged and Surf scoters with more yellow-gray legs, the range of variation in leg color for all three species (which is probably temporal) includes gray, so I believe that this bird is unidentifiable from this image (but note below).

That leaves the two pink-footed birds in the middle, neither of whose heads can we see. Among scoters, Black Scoter is unique in many ways, with foot color being one of the more obvious, at least for birds in flight. The other two ABA-area species [Common Scoter has not been accepted as occurring on this side of The Pond, yet, but should certainly be looked for on the East Coast] both sport pink or orangish-pink legs, with White-winged tending toward the more-orange end of the spectrum of leg color in the two species. So, does the dark pink leg color indicate that these two birds are Surf Scoters? The color may be suggestive, but we should endeavor to confirm that suggestion. Of course, without any heads to ogle, we aren't left with many ways to do so, other than the obvious: White-winged Scoters have white secondaries. In the below version of the quiz picture, I have labeled the two pink-footed scoters as PFS1 and PFS2 and also pointed out one of the wings on each of the two birds.

On PFS1, only one wing is visible, the other wing being hidden behind the body; on PFS2, both wings are visible, though only one is pointed out. Of the pink-footed birds, on only one of the three visible wings can we see any secondaries -- the one pointed out by 'PFS2 wing.' On this wing, the primaries are curled down from their meeting with the secondaries, the outer two or so of which we can see well enough to call them black, rather than white. This bird, then, is an adult male Surf Scoter. What the other one is, however, is not definitively knowable from this part of the larger picture, which I include, below. In this version, which shows all the birds that are in the original picture, the pink arrow points to the head of the bird that, for the quiz, we need leave unidentified. Obviously, the bird is an adult male Surf Scoter. The head of the Surf Scoter in front of this one is the head of the unidentified juvenile scoter in the quiz image; it is also a Surf Scoter.

Eight responses included only one species, all omitting Surf Scoter. Additionally, one response had one too many 'o's in "Scoter" in both correct species ("scooter"), so was precluded from being correct for the competition.

Incorrect species provided as answers:
White-winged Scoter - 3

Congratulations to the 19 of 30 getting the quiz correct:
Kirk Huffstater
Thomas Hall
Aaron Brees
Ben Coulter
Pam Myers
Nick Komar
Megan Miller
Logan Kahle
Devich Farbotnik
Chris Warren
Su Snyder
Peter Wilkinson
Joe Bens
Ben Griffith
Bryan Guarente
Tyler Bell
Sean Walters
Diane Porter
Chishun Kwong

Answer: Surf Scoter, Black Scoter