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QUIZ GULL #5 (answer below)


ANSWER:

The correct answer to Quiz Gull #5 is Glaucous-winged Gull. Let's age the bird first. It's clearly not an adult, but not a first year bird either. It looks pretty typical for second year, with its "adult gray" back and scapulars, but otherwise immature by virtue of black bill tip, lack of adult gray on the wing coverts, and smudging down the underparts. Looking at how worn (and probably faded) the bird's feathers are, it's probably safe to say this is a late spring or summer bird, so second summer. Turning now to the white primaries, we immediately shorten our list to the pale-winged gulls: Glaucous, Iceland, possibly Glaucous-winged. Thayer's is not likely to fade this much. Slaty-backed may fade this much, but is eliminated anyway due to the mantle shade. Focussing now on bill shape: it's large with a pronounced gonydeal bulge, very typical of Glaucous-winged (and Western and Yellow-footed). Iceland is immediately eliminated there. Glaucous has a straighter bill. Being generous, we are now down to Glaucous and Glaucous-winged. The bill shape strongly favors Glaucous-winged. The bill coloration looks like a ringer for Glaucous. However, this is a second year bird, when this pattern is possible with most species. Also, the way the black comes in along the cutting edge so much is probably excessive for Glaucous. The smallish rounded head is better for Glaucous-winged than Glacuous (though don't bet the farm on head shape; I've seen Glaucous look like this). Likewise, the mantle shade is fine for Glaucous-winged, but too dark for Glaucous. The dark eye is the same; we'd expect a pale eye by now on Glaucous. Finally, the white coverts and nearly white primaries do occur on Glaucous-winged Gulls in late spring and summer, when they are quite faded. Check out this page for more examples of faded Glaucous-winged Gulls that are equally faded and white. Technically, it would be hard to rule out Glaucous x Gl-W, but I don't think we need to get into hybrids to find an answer.

This photo was taken May 4 by Don DesJardin (copyright 1998) in Santa Barbara, CA.


This proved to be a more difficult quiz than I thought, but some West Coast birders nailed it, correctly guessing the species, plumage, and even the month and location ("southern Calif.") of the photo!

GUESS # OF VOTES
Glaucous-winged Gull (35% correct) 8
Glaucous Gull 7
Iceland Gull 1
Herring Gull 1
Glaucous x Herring Gull 2
Glaucous x Glaucous-winged Gull 2
Glaucous-winged x Western Gull 2