Al Jaramillo wrote:
> Since I moved over here to Vancouver I have had the pleasure of seeing
>4 or 5 Glaucous gulls. All of these birds were close to being white, but
>all of the ones that I saw well were first winter birds. Usually these
>very pale birds are reported as second winter birds, probably because
>Peterson illustrates second winter birds as being white. All of the
>local birders that I asked about this mentioned that almost always
>wintering Glaucous Gulls are in this white plumage.
> Back in Ontario, where I used to live, Glaucous Gulls were more common
>than they are here and we did not see this high a number of white birds.
>First winter birds back east come in two main types: creamy brown birds with
>a lot of barring as well as very pale birds that quickly wear to a largely
>white plumage.
> As I understand it, birds here should be of the Alaskan _barrovianus_
>subspecies which are supposed to be smaller than other Glaucous Gulls.
>Now my question is are they also much paler as immatures than eastern
>birds? What do most of the Glaucous Gulls observed in Washington look
>like? Are they also whitish, or do darker birds appear every so often.
>Is my impression that western Glaucous Gulls are paler just a 'sampling
>error' or is this real?


Never one to let a Gull thread drop, I was going to reply that I didn't
think northwest Glaucous Gulls were any paler in my experience. At least when
compared with the Glaucous Gulls I'd been used to seeing along the
Mississippi River. But before posting my reply, I decided to wait until I
could go
through my slides in order to quantify my assertions. Well, I've just done
that and I may have to change my thinking. I selected slides of a total of
12 first winter Glaucous Gulls, all photographed in Oregon, and all taken in
December or January. (I ignored the ones taken later, because those birds
all looked rather faded and worn.) I compared the 12 with the photographs
in Grant's 2nd edition. Here are my results:

Three are lighter than the bird in figure 399, page 304 (his palest bird).
None are as dark as the first summer bird on the right in figure 412, p 308
(the darkest bird, but wrong plumage). One looks about as dark as the fairly
dark Irish bird in fig 401, p 304. The remainder are all somewhat lighter than
the intermediate bird in figure 400, ranging to as light as the light bird
in figure 304.

What can I conclude? Well I don't know if the photos in Grant are
representative, since his are all European birds, but my quick experiment
might suggest that our birds may in fact be somewhat paler than average.
Another thing I noticed, which may be more significant, is that all the birds
I photographed have pure white primary tips, while only one of the first
winter birds in Grant does. Could it be that we 'miss' the dark Glaucous
because we've got Glaucous-winged to contend with? (Perhaps that's the
sampling bias you referred to?) I've got a couple of other photos of
dark birds with white primary tips (none of the photos are too great,
unfortunately) which I believe to be hybrid GxGW, though I suppose it is
possible that one or both are instead dark Glaucous Gulls.

As to size, I've noticed two distinct size groups. I used to think the small
ones were of the Alaskan race, and the big ones from further east. Now I
think they might all (or almost all) be Alaskan birds; and that there must be
a huge amount of sexual size dimporphism. The big ones are by far our
(Oregon's) biggest gull. The small ones are often as small as a medium
sized Glaucous-winged, and often they have a Herring Gull sized bill as well. I
might be mistaken in this (too) since less that 50% seem to be of the small
variety.


Gene Hunn wrote:
>I've been using the eye color feature to distinguish 1st winter Glaucous
>Gulls (dark eyes) from 2nd winter birds (light eye), though I suspect
>this may not always work. By that standard we get mostly 1st winter
>birds, even some very pale birds others have labeled 2nd winter on the
>assumption that they were too pale. Is this what the rest of you'all think?

I usually go by the pattern and color of the back, rather than the eye color.
I've definitely seen birds that had backs which had moulted to pale gray,
indicating they were at least 2nd winter birds, while still retaining dark
eyes. Of all the mid-winter birds labeled "pure white" by others, I have
always been able to see at least a hint of either the spotted 1st year back
pattern, or a very pale gray adult back pattern. Even of those, most turn out
to be first winter birds. (I would guess that at least 80% and possibly more
of all our Glaucous Gulls are first winter birds.)

By March, all bets are off, as almost all of them seem to have faded out to
look "pure white".

Skip
--
Skip Russell, Beaverton, Oregon
skipr at teleport.com