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Saturday, January 16, 2010

Gull ID Quiz Answers

"Gulls - a word of inherent paradox. Almost anyone can recognize a gull - or "seagull" - as such, but to identify certain gulls to a species can vex the most experienced observers. Gull identification offers something for everyone - form studying the different plumages of Laughing Gulls at a beach parking lot to puzzling over winter flocks of large gulls at a river mouth or reservoir. You can take identification to any level you choose, and there's still an unknown, a new frontier, another question to be answered. That's what makes gulls so much fun."
- from the Gulls of the Americas field guide

Gulls can be difficult enough to identify as purebred adults, but add in all the cycles they go through before they reach adulthood and all the hybridization that occurs and distinguishing one species from another becomes downright complicated. I knew this already, but it was reinforced by spending time with gull field guides and the varying answers I received on the quiz both in the comments on my last blog post and in the several e-mail answers people sent me. Thanks to everyone who responded, particularly the ace birders who gave some great insight into how to ID gulls.


The only thing everyone agreed on was that the gull in photo #3 (click on the images or refer to the previous post to see larger photos) was a glaucous-winged gull. The pale gray wingtips and dark eye are key field marks for this species. Most also pegged it as a third winter bird, which is where I placed it as well. While the plumage is fairly clean, this one is clearly not yet in adult in part because of the black tip to the beak, since adults have a red spot on the bill.


For the bird in photo #2, several people guessed it was an adult Thayer's gull, and others an adult western gull, but I concluded it was an adult Western x Glaucous-winged hybrid. The legs are actually relatively pale (Thayer's have deep pink legs) and appear a bit darker in the photo because they are cast in the shadow of the bird. As Greg pointed out, the bill is fairly stout, which also points away from the Thayer's which has a smaller bill that's more yellow-green than yellow-orange in color....or so the field guides tell me! There are many paler western gulls, but the fact that the mantle is light combined with the dark (but not quite black) wing tips led me to conclude this was a hybrid with the glaucous-winged gull. The western x glaucous-winged hybrid is very common in the Pacific Northwest.


Everyone knew this wasn't an adult bird, but the species suggestions ranged from Thayer's gull to mew gull to ring-billed gull. I had concluded this was a first winter ring-billed gull, an identification helped, I admit, by the fact that there were many adult ring-billed gulls around and no mew gulls when the photo was taken. I didn't know to look for the "dark anchors" as pointed out by Greg and Dave - they're referring to the dark centers on the feathers in the brownish wing coverts, which are uniformly pale brown on the immature mew gulls.

I definitely learned a lot more about the nuances of gull identification with this little quiz, and I hope you did too. I think it's an experiment that bears repeating sometime in the future with some new gull photos!