Mystery Bird: Western Gull, Larus occidentalis

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[Mystery bird] Western Gull, Larus occidentalis, photographed in Monterey Bay, California. [I will identify this bird for you in 48 hours]

Image: Joseph Kennedy, 6 May 2010 [larger view].

Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/1000s f/8.0 at 1000.0mm iso400.

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

This challenging mystery bird resides on the western coast of the USA -- the individuals in Seattle are much paler in appearance than the ones in California, such as this bird. Can you name the species?

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I believe that's known as a Monterey Sea Gull. I used to live in the Monterey area (Santa Cruz) and it looks familiar, albeit I've never been too certain what either its common or scientific name is. On the other hand, that was multiple decades ago, so I could easily be misremembering and/or more confused than usual.

In any case, it's probably not a brickâ¦

I'd have sworn this was an east coast gull, named for an oily, bony fish that's often salted and pickled, but the west coast location made me doubt myself. So I went to Cornell and found that the species is on the west coast, too! As a result, final answer... it's a Clupea!

I'm not so sure about the Clupea, apikoros. I don't like the darkish iris for that species, and the bill seems too thick, though not thick enough for the gull who's becoming milky white. I like this best for the strictly coastal guy.

By Pete Moulton (not verified) on 14 Jun 2010 #permalink

Just a question, but I *think* the function for the red spot on the lower bill is to give it's chick an aim point to simulate regurgitation. Am I correct in this?

Pete,
As I said, I'm pretty much limited to east coast in direct experience and that's the bird that popped when I saw this pic. I was surprised that had a continent-wide distribution. Yes, the eye color is darker than usual and the yellow lids are more pronounced. I chalked that up to "regional variation" (i.e FLKWUD*). I tried looking up "Monterey Gull" as blf proposed, but saw no species of that name.

After going all the way through the list of "regularly occurring" gulls on this page, it could very well be a Glaucous-winged Gull or possibly (but unlikely) a Western.

*Funny looking kid with unknown diagnosis

I'm looking at pictures, and trying to figure out. I wonder how good bill rings and spots are for identification? Most of the pictures of gulls with red dots on the beak seem to also have a dark/black bit or ring ahead of the red dot. But the Western gull seems to have the red dot only in the picture I'm looking at.

The white head would suggest a mature bird. The eye seems more fleshy-ringed than I'm seeing in other pictures, though.

It's easy to say "I don't do gulls" but I keep trying. In looking at this gull, it seems to me that it has an unusually sloping forehead, giving it a gentle look--not the usual fierce look of the larger (heavier?) gulls. Is there a clue there?

I'm struck by those red-rimmed eyes. The white head suggests a mature bird. It's like a kelp gull, except that the eyes are dark rather than pale. That leads me to guess that it is the Cape gull, Larus Vetula.

Echidna -- this is a bird where the location really matters -- I don't think Cape Gull has ever been recorded in the US.
Bardiac -- most of the large white-headed (European and N. Am.) gulls have just the red spot in breeding condition.
Murray -- That sort of field mark is useful, with the caveat that it can be affected by various things (missing feathers, posture, etc.), so especially in a photo, it's worth being cautious with.
I think you all missed an important clue -- Grrl said that birds from Seattle are paler than this bird. Western Gull has two distinct subspecies, with the northern being paler than the southern one. In fact, I think Monterey Bay is just about where the two forms meet. Looking back, seems to me that Pete nailed it.

Well summed up Paul, I think the only other bird to consider is Glaucous-winged but doesn't it have a pale iris as an adult? I don't think that there are any features shown to support a hybrid between the two so I'm with you on this one.

Eye color in Glaucous-winged can be rather variable (probably due to introgression with other species -- GW's seem to be particularly prone to forming hybrid zones). To tell the truth, I'm relying mostly on the location, age of the bird, and date. This is a breeding condition adult -- and the nearest breeding range for GW is Washington State (where they're almost all GW X Western hybrids, anyways).

I brought up the hybrid problem because I have seen several of them at Ventura in November. I thought that they may linger in the area.

Well, Adrian, if you do have adult hybrids hanging out, then I don't know how to ID this bird specifically. I know that up in Washington I wouldn't want to have to ID any of these -- apparently most are hybrids, with plenty of backcrossing.