Re: Retraction

Nick Lethaby
 

There may be three birds involved here. There is a bird with classic Thayer's plumage. There is a bird that I feel is definitely a hybrid based on good photos and seeing it well in the field. Joan's photo may be that hybrid but may well not be. It shows some scapular molt, but probably not as extensive as on the hybrid.

Also nothing is definite here. Based on when I used to look a lot at large gulls in the Bay Area, I believe that many GWxHerring can look identical to Thayers in 1W plumage. You then get into the whole structure issue. But how do you know if a 'giant Thayer's' is an extremely large Thayer's or a GWxHerring hybrid. Also some female Herring and GW gulls can get quite small as well. So I would contend that it is very difficult to be sure on individual gulls. When you are in a location that has more Thayer's, there will be plenty of females around that are obvious on structure and it's safe to assume that the majority of the more ambiguous are Thayer's too. I don't think we can do that down here most of the time as Thayer's are very uncommon.

On Wed, Jan 15, 2020 at 10:48 PM Conor Scotland <scotland.conor@...> wrote:
Would love to hear what reasoning is behind the hybrid theory. I think the gull looks like a pretty classic Thayer's gull, though hard to be certain without seeing the primary tips better. In my experience, GWGU x HERG hybrids usually have larger bills and somewhat disproportionate-looking heads. This bird's head has the delicate look of Thayer's. Would also expect some more scapular molt to have happened by now if it was the hybrid, but I think we're seeing 1st cycle scapulars still on this bird, which I believe is also good for Thayer's. I could be quite wrong, and GWGUxHER can often look extremely similar to Thayer's, but am just curious why it's a hybrid.

Thanks,
Conor

On Wed, Jan 15, 2020 at 9:02 PM Joan Lentz (cox.net address) <joanlentz@...> wrote:
Hi Folks:  Guess what?  There are at least 3 individual gulls near the dam area at Lake Los Carneros that might be candidates for Thayer’s Gull, & my list posted yesterday said that I had a Thayer’s/Iceland Gull.  Upon consultation with various people, it appears that my candidate is better for a hybrid (sigh) Glaucous-winged x Herring Gull.  If you can find Hugh Ranson’s portrait of the Thayer’s Gull, as well as Santiago Lupi’s, those are truly Thayer’s/Iceland Gull, which was seen on the CBC.
        Back to the drawing board…..as they say…..

        Joan Lentz




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Nick Lethaby
Goleta, CA

Mobile: 805 284 6200
Work: 805 562 5106

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Nick Lethaby
Goleta, CA

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