Subject: Re: Slatey-backed Gull and Dickcissel
Date: Feb 23 20:35:31 1996
From: Alvaro Jaramillo - alvaro at quake.net


Russell Rogers wrote:
>
>It was about the same size as the GW Gulls. The mantle seemed to be a
>shade or two lighter than the wing tips. The head had a good amount of
>streaking on it and the eye seemed fairly dark. The bill was very yellow.
>It was a little to far away to get a good line on the shape of the bill,
>but the head and over all build was slimmer than the GW Gulls which it
>sat next to. I also couldn't get a good look at the white-spots on the
>primaries. None-the-less, I am sure this was the Slatey-backed that was
>first reported back around Christmas.

This is a very general description, but it does not sound like a
Slaty-backed Gull to me. Slaty-backed Gulls, as adults, should have pale
yellow eyes, nearing whitish-yellow. The bills are not bright yellow, but
pale yellow like a Herring Gull, I am unsure about what 'very yellow' means.
Given the rarity of this species, I think that it is premature to make the
identification without seeing diagnostic features such as the wing pattern,
in addition to the bill structure. Just and opinion :-)

>
>The bird has been reported as a female in winter plumage. I belive this
>in error. The bird has quite an extinsive black bib, which females would
>not have in any plumage. Imm. males would not have any black as well.
>Immature birds should be moulting into alternate plumage at around this
>time. However, it has very bright rufous lesser wing covers, which are
>very subdued on imm. males. Eventhought the bird was fairly close, I
>could not get a good look at the shape of the tail feathers, which is
>also a good indication at to its age (pointed and narrow tail feathers
>on an imm.).

I had a good look at a series of specimens a while ago and discovered that
young males in fall are quite difficult to separate from adult females.
However, adult males do not have a noticeably different 'winter' plumage,
they appear just a little duller than in the breeding season which does not
sound like this bird. If it is really yellow on the breast and has lots of
black on the throat then its an adult male, but the yellow has not been
mentioned and I imagine that it would be difficult to confuse an adult male
with a female. The extensive black on the throat and bright rufous on the
coverts does not necessarily exclude a young male particularly if it has
begun its prealternate moult.


Alvaro Jaramillo "You are better off not knowing
Half Moon Bay, CA how sausages and laws are made"
alvaro at quake.net Otto von Bismarck,
but I saw it in a fortune cookie!

http://www.quake.net/~alvaro/index.html