Western Gull

Mystery Bird: Western Gull, Larus occidentalis

grrlscientist — Mon, 14 Jun 2010 07:59:29 +0000

Mystery Bird: Western Gull, Larus occidentalis

tags: Western Gull, Larus occidentalis, birds, mystery bird, bird ID quiz

~~[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?

Review all mystery birds to date.

grrlscientist Mon, 06/14/2010 - 03:59

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.

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.

Mystery Bird: Western Gull, Larus occidentalis

grrlscientist — Wed, 25 Nov 2009 08:59:35 +0000

Mystery Bird: Western Gull, Larus occidentalis

tags: Western Gull, Larus occidentalis, birds, mystery bird, bird ID quiz

~~[Mystery bird]~~ Western Gull, Larus occidentalis, photographed at Pt. Reyes, California. [I will identify this bird for you in 48 hours]

Image: Joseph Kennedy, 21 December 2007 [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.

Review all mystery birds to date.

grrlscientist Wed, 11/25/2009 - 03:59

Not as esay as I first thought...

Western Gull, Larus occidentalis: large gull with white head and body, and gray wings; yellow bill with a red subterminal spot.

Differentiated from the very similar Slaty-backed Gull, Larus schistisagus which tends to have relativly thinner bill and "more dirty markings on head in winter" (Cornell), and the Glaucous-winged Gull, Larus glaucescens, which is a paler gray on back and gray wingtips.

Identification can be hard as both the Western and Glaucous-winged Gulls hybridize and intermediates are common.

I can't see any characteristics of hybridisation here, it looks like a "good" Western Gull of northern California to me. However is there any study to see if there are any pure gulls in this complex without any hybrid genes (rather like Rock Dove here in UK)

I agree that this is a "good" Western Gull. Another supporting field mark is that the photo was taken in December when other white-headed gulls would usually show some streaking or smudging on the head. Westerns retain their clean white heads year round.

Good diagnosis, David. Just to extend it a bit -- the back is too dark for any Herring Gull, and a Lesser Black-backed would show more primary extension behind the tail, a thinner bill, and a yellow eye. The darker eye and medium gray mantle point to the northern subspecies, occidentalis, as does the location.

2 further points regarding Slaty-backed Gull. First, they should be noticeably darker-backed than this, more like a southern Western Gull. Second, I don't believe that they show the "drooping skirt" that Westerns do. (That term refers to the extensive white visible on the secondaries when the wing is folded -- in most gulls the secondaries are shorter and the white vanishes behind the coverts.) Of course, I've only seen two Slaty-backeds, so I could be off-base there.

The situation is made more complex by the propensity of the Herring Gull to also hybridize with the Glaucous Gull (in Iceland), the Glaucous-winged Gull (in Alaska), and the Slaty-backed Gull (in Siberia). In turn, the Glaucous and Glaucous-winged gulls hybridize around the Bering Sea. Furthermore, the Iceland Gull hybridizes with Thayer's Gull (on Baffin Island)!

Some interesting research includes:

Bell D.A. Genetic differentiation, geographic variation and hybridization in gulls of the Larus glaucescensâoccidentalis complex. Condor. 1996;98:527â546.

Crochet P.A, Chen J.Z, Pons J.M, Lebreton J.D, Hebert P.D, Bonhomme F. Genetic differentiation at nuclear and mitochondrial loci among large white-headed gulls: sex-biased interspecific gene flow? Evolution. 2003;57:2865â2878.

and VigfÃºsdÃ³ttir, F., PÃ¡lsson,S., and IngÃ³lfsson, A. Hybridization of glaucous gull (Larus hyperboreus) and herring gull (Larus argentatus) in Iceland: mitochondrial and microsatellite data. Philos Trans R Soc Lond B Biol Sci. 2008 September 12; 363(1505): 2851â2860

And let's not forget the ring species model as presented by Ernst Mayr: the Herring Gull L. argentatus, which lives primarily in Great Britain and Ireland, can hybridize with the American Herring Gull L. smithsonianus, (living in North America), which can also hybridize with the Vega or East Siberian Herring Gull L. vegae, the western subspecies of which, Birula's Gull L. vegae birulai, can hybridize with Heuglin's gull L. heuglini, which in turn can hybridize with the Siberian Lesser Black-backed Gull L. fuscus.

The Lesser Black-backed Gulls and Herring Gulls are sufficiently different that they do not normally hybridize thus forming a circumpolar species "ring".

Although there is recent evidence that this complex may no longer fit that model: Liebers, D., de Knijff, P., and Helbig, A.: The herring gull complex is not a ring species. Proc. Roy. Soc. B 2004; 271(1542):893-901.

Rather annoyingly, and certainly not for the first time, a prior comment concerning hybridization was apparently accepted for review but never materialised, so I will re-post but having had to remove a few html href attributed references to avoid detention:

The situation is made more complex by the propensity of the Herring Gull to also hybridize with the Glaucous Gull (in Iceland), the Glaucous-winged Gull (in Alaska), and the Slaty-backed Gull (in Siberia). In turn, the Glaucous and Glaucous-winged gulls hybridize around the Bering Sea. Furthermore, the Iceland Gull hybridizes with Thayer's Gull (on Baffin Island)! Some interesting research includes:

Bell D.A. Genetic differentiation, geographic variation and hybridization in gulls of the Larus glaucescensâoccidentalis complex. Condor. 1996;98:527â546.

And more recent research here:

VigfÃºsdÃ³ttir, F., PÃ¡lsson,S., and IngÃ³lfsson, A. Hybridization of glaucous gull (Larus hyperboreus) and herring gull (Larus argentatus) in Iceland: mitochondrial and microsatellite data. Philos Trans R Soc Lond B Biol Sci. 2008 September 12; 363(1505): 2851â2860