In reply to Bob Norton's question

It's usually pretty easy to see as the wingtips project (sometimes sort of
partly sideways) and cross each other above the tail at the rear of the
bird. Of course, the underside is usually a bit shadowed so may appear
darker than it really is. I've also been able to pick out sitting Little
Gulls from Bonaparte's this way, as the blackish underwing of the Little
Gull shows up quite conspicuously.

On immature Thayer's Gulls: My impression is that they are relatively far
less common up here than are adults, but that the situation is reversed in
California (typically immatures winter further from the breeding grounds,
probably because they can't compete with the adults for the better
habitats). So I don't see that many. It's much more a matter of judging size
and shape and color, all of which are matters of degree and best seen with
direct comparisons with known birds of other species (or accompanying
adults). So look for a brownish gull with pinkish-flesh feet (which most 1st
years gulls have, even those that have yellow feet as adults), duller than
adults. The bill should be all dark (unlike first year California Gulls and
Glaucous Gulls, which are two-toned) and the eye also. Size noticeably
smaller than Glaucous-winged types and somewhat smaller than any Herring
Gulls that might be around (on average), but larger than a Ring-billed or
Mew (size of California Gull but not as "long"), with relatively slight bill
and rounded head relative to Herring, Glaucous-winged, Western, or hybrids
among those species. The coloration is paler than Western or Herring (which
tend to dark browns and blackish primaries), more or less Glaucous-winged
shade but in my recollection more tan than grayish. The primaries should be
more or less the same tone as the body feathering and, if the plumage is
fresh, the primaries will be neatly margined by whitish buff (and the
coverts also neatly patterned). In flight the secondaries and tail are
darker than the body. A Kumlien's Iceland Gull should show distinctly
whitish primaries (but beware of the effects of wear late in the winter or
in early spring) and tend to have an even daintier bill. There are still a
percentage that don't pan out.

Gene Hunn.



>In the message dated 97-10-29 05:38:25 EST, you wrote:
>
><< Finally, check to see if the black on the wing tip is limited, that is,
>less
> extensive and more interrupted by white "windows" than is normally the case
> with Herring and Ring-billed Gulls (which have mantles as pale or slightly
> paler than Thayer's) and that from the underside the primaries look pale
> gray, not blackish (as in Herring Gulls). You can see this best in flight
> but it is also noticeable when the bird is standing or sitting as you can
> see the top of the wing and front and the underside of the tip of the wing
> in back, which should appear pale.
> >>
> I need a little help on how you can see the underside of the tip of the
>primaries on a sitting or standing bird. How close do you have be with a
>scope or binocs do you have to be to see this? Does the bird have to be
>facing at least partially away from you or can you see this in a bird
>broadside to you?
> Personally, I would be delighted if you would expand on immature Thayer's
>plumages. I suspect I am in a minority (a good lady birding friend said to me
>one day, 'well if we go there I want you to promise me that you won't make me
>do gulls).
>
>Bob Norton
>Joyce, WA
>
>