Tuesday, July 13, 2010

The rattiness makes it fun

I have to warn you. If you're a birder who would be just as happy leaving them all as "seagulls" even in December when the gulls are freshly plumaged then it's time to navigate your browser back from whence you arrived.

If you're a birder who's trying to fight the summer doldrums by taking on whatever ID challenge may be offered, then I give you (drumroll please) a ratty summer gull.

I first noticed this bird about a week and a half ago when it flushed in front of me as I was walking the water's edge with one of the girls. When it flew, the wings seemed really dark and I thought it might be a Lesser Black-backed Gull, but when it landed it looked a lot like the other Herring gulls. Lacking scope or camera, I proceeded down the beach to make sure that a distant group of Willets contained only Willets.

Tim and I saw the bird again a couple days ago but couldn't get all that excited about it (especially given that he's already nicely photographed a clear 2nd calendar year Lesser Black-backed a few weeks ago). Yesterday though, I said I didn't care what I saw, I just wanted to get some bloggable photos, I'd even take that Lesser Black-backed/Herring thing. As luck would have it, Tim said it was right down there on the beach. Lacking anything else to do, we walked down.
The long primaries, tertial pattern, and dark bill definitely gives it a Lesser Black-backed gestault. When I looked at it closely in the field I thought the gony angle was too heavy for it to be Lesser Black-backed. I've made this mistake before, of focusing too much on a single field mark, but that didn't stop me for doing it again. I concluded it was a weird Herring Gull and stopped studying it. Only when I studied the pics did I also note the the leaner body size and head proportions, the leg color, and a few other features.
Note in this picture that the long-winged look is doubly accentuated by moult since our bird on the left essentially lacks a tail while the Herring Gull in front of it lacks its outer 2 primaries.

The time had come for flight shots so Tim walked slowly into the flock and several of the birds picked up, hooked past me, and re-settled 30 yards away on the beach. The freeze frame makes the ID much easier. While we debated whether slaty colored feathers were coming into the mantle with the bird at rest, we can see a nice row of grearter coverts showing the typical slaty color of a Lesser Black-backed, as well as along the leading edge of the wing. Howell and Dunn also point out that correspondingly aged Herring Gulls have contrastingly paler inner primaries, as exhibited by both the lead and trail birds in this photo. Note that on all of these birds the inner primaries are fresh 2nd cycle feathers. Our bird's secondaries and outer primaries are retained first cycle feathers.

The next photo shows the underwing and the yellower leg color. Olsen and Larsson call attention to the darker underwings of Lesser Black-backed's of this age. Comparing it to the Herring Gulls above, I would say that applies in comparison to the trail bird, but not as markedly to the lead bird.

Just in case there's other readers who shared my misconception of Lesser Black-backed not showing much of a gony angle, here's a montage of some of the heavier-billed Lessers that I have in my collection of photos. The upper right bird is from Berrien, the rest were all shot in Virginia Beach.
Jon posted a note a few weeks ago saying that it's been a decade since Lesser Black-backed has been found summering in Berrien; assuming that a bird seen in New Buffalo was different from either of the Tiscornia birds, there's been at least 3 this year.

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