Gene,
Thanks for the good discussion and I have no quarrel with anything you
wrote and the last paragraph is a new thought for me and I have a question.

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