Mystery Bird: Lesser Black-backed Gull, Larus fuscus

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[Mystery bird] Lesser Black-backed Gull, Larus fuscus, photographed in Quintana, Texas. [I will identify this bird for you tomorrow]

Image: Joseph Kennedy, 2 March 2009 [larger view].

Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/1250s f/8.0 at 1000.0mm iso400

Please name at least one field mark that supports your identification.

Rick Wright, author of Aimophila Adventures and Managing Director of WINGS Birding Tours Worldwide, writes:

Yes, it's a gull -- but don't panic. I think you'll agree that this is an easy one as large white-headed gulls go.

How do we know it's large? The long tarsus, heavy bill, and angular head doesn't really fit any of the small gulls. And white-headed? The various 'hooded' gulls show discrete patches of dark on the head in non-breeding plumage, rather than the scattered flecks and streaks of our quiz bird.

That out of the way, let's start at the rear of the mystery creature. I can just barely make out the edge of the white tail beneath the folded wingtip -- and the tail falls far short of the wingtip, making this bird look distinctly long-winged, decidedly "scissor-tailed" (remember that the black we're seeing is the wingtip, not the tail). Many large gulls are quite blocky in the rear, far less slender in general shape than this bird.

A closer look at the wingtip, focusing on the bird's left wing, shows us that the long outermost primary has a black tip with a larger subterminal white spot, ruling out gulls such as Great Black-backed where the white goes all the way to the tip of the primary. The tertials are broadly white-tipped.

The back is dark, a charcoal gray notably darker than Ring-billed, Herring, or most California Gulls, but notably paler than any of the truly black-backed gulls such as Great Black-backed or Kelp. At this point, the long wing-tip, the pattern of the outermost primary, and the mantle color should make us think of a Lesser Black-backed Gull, and we'll keep moving forward with that possibility in mind.

Foot color? Yellow, consistent with Lesser Black-backed but not typical of the other dark-backed species. Head plumage? Streaked and spotted, unlike the immaculate whiteness of Great Black-backed. Eye color? Clearly pale, again appropriate for Lesser Black-backed but wrong for California and for (most) Great Black-backed Gulls.

The bill is slender at the base and long, but with a noticeable gonydeal angle and hook to the upper mandible. There is a diffuse red spot on the lower mandible and some dark smudginess on both mandibles, suggesting that this Lesser Black-backed Gull may not yet be fully adult.

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From the yellow legs and ringed bill, I'm going to say it's a ringed bill gull. But really, all these damned gulls look so much alike, I'm surprised they themselves don't accidentally shack up with the wrong species half the time. Of course, this one's not in its breeding plumage, so I guess that doesn't matter. ;-)

Lesser black backed gull

The red marking on the beak, dark grey back, yellow legs. Just a guess here though.

Well, technically, they _do_ shack up with the wrong species a fair amount. Hence the need to think about hybrids.

The pale iris and the ring on the bill argue for ring-billed gull, I agree. But there are some problems with that, too. The mantle seems awfully dark for ring-billed to me, and the red spot on the bill is bothersome. If it weren't for that pale iris, I'd say this bird looks more like a California gull (though even there, the mantle seems on the dark side to me). I don't know; maybe a ring-billed X California hybrid? Or a ring-billed X something else?


By Alf Rider (not verified) on 13 Apr 2009 #permalink

Except for the light eye, this bird is almost a perfect match for the pic of the "Adult nonbreeding Great Basin" California Gull, p. 215 in the big Sibley. Given that gulls seem to care very little for the species lines people define, I'd be happy to believe in a California X Ringbill cross....

Yellow legs, very long projection of the folded wings beyond the tail, dark but not black back and upperwings, lots of uniform fine streaking on the head and neck, yellow eye, fairly large red spot on the bill. It's a (near) adult Lesser Black-backed Gull.

I think the bill is far too...vicious looking for a ring-billed gull, and the back is much too dark.

Somewhat fits a California gull, except for the piercing, pale iris, and the golden yellow legs.

But maybe Lesser Black-backed gull is the best fit (for the reasons California gull doesn't).

Unless it's a hybrid gull...

Lesser Black-Backed Gull was my immediate reaction. They're quite common round here: I used to see them nesting on the rooftops around my office, (back when I had a job).
Colours right for an Icelandic visitor - a bit lighter than the Scandinavian ones. Dirty colour of the head says it's not quite mature.

Could be a hybrid, but I wouldn't have thought it's likely. I don't think that the LBG breeds with the American Herring Gull and it looks too dark for a European/American Herring Gull hybrid.

I don't know where Quintana, TX is but I'm looking at Sibley and there's a green dot way at the tip of Texas on the map for the Black-tailed Gull. This bird's beak has black and red tip, it has yellow legs, pale iris and the coloring resembles the Black-tailed Gull.

This looks like a hybrid gull that both Cornell Laboratory of Ornithology and Schoals Marine Laboratory have been studying. They've witnessed mating of Lesser Black-backed gulls and Herring Gulls, and they've each been tagging and following both species and their hybrid offspring as well. Here's a link with info and photos, in case you're interested: