Hi, Beverly –
I disagree with Alan about this bird in some respects. I would not identify
it as a Slaty-backed from these photos, but consider it suggestive. It is hard
to call any bird a Slaty-back without seeing the wingtip patter, pretty much
hidden in these photos. The one photo that does show wingtips somewhat, above
the shoulder of the Herring Gull, shows a lot of white – possibly more than
typical of Western. The same photo seems to show a clear, very pale iris
consistent with Slaty-backed. Alan is correct that winter Slaty-backs have a
more hooded look, but this is the end of February, and many of the gulls with
winter hoods (e.g., Glaucous-winged, California, Mew, and Herring) have begun
to replace the darker feathers with the white of summer plumage, so a
Slaty-back at this date might have less hood than it did a month or two ago.
Some of the details of shape and leg color look a bit more like Western, as
Alan suggests, but I do not see any of them as definitive.
I also disagree with Alan’s suggestion of dubious ancestry. Certainly some of
the Western-like gulls on the Oregon coast have Glaucous-winged Gulls in their
family tree. Those birds (adults) tend to also be intermediate in mantle
color; i.e paler than “pure” Westerns. Westerns vary geographically in mantle
color, paler here at the northern end of their breeding range, and
progressively darker to the south (although quite a few of the darker southern
birds move north when not breeding). This bird and other birds with darker
backs than our residents are unlikely to get their winter head markings from
Glaucous-winged Gull ancestors. Instead, it’s pretty clear that a minority of
adult or near-adult Westerns do develop some dark color on their heads in
winter.
Here is one explanation that I have provided in the past. Sub-adult Westerns
(3-4 year olds) often have heavy winter hoods. They also have some black in
their tails, and often in their bills, some brownish primaries, and other signs
of immaturity. It appears that a few of these bird may continue to develop
some of the winter head pattern after reaching adulthood, when most Westerns
retain pure white heads. I do not like to assume mixed ancestry for these
birds unless one or more other characters also appear intermediate (iris color,
eye-ring color, mantle color, bill color).
Wayne
From: obol-bounce@xxxxxxxxxxxxx [mailto:obol-bounce@xxxxxxxxxxxxx] On Behalf Of ;
Alan Contreras
Sent: Sunday, February 28, 2016 11:53 AM
To: mapsout@xxxxxxxxxxx
Cc: OBOL
Subject: [obol] Re: Nehalem Bay-Dark smokey gull with smudgy eye - Slaty-backed
or Olympic??
I think if this were a Slaty-backed it would have brighter red-pink legs, a
more “hooded” look with lots of speckles, probably a yellower eye and probably
a somewhat smaller bill. So my vote goes to Western with a dubious grandparent.
Alan Contreras
Eugene, Oregon
acontrer56@xxxxxxxxx
On Feb 28, 2016, at 11:47 AM, Beverly Hallberg <mapsout@xxxxxxxxxxx> wrote:
Hi all,
Yet another gull question (sigh)... Maybe you could help id this dark gull
that was just south of the Nehalem Bay SP boat launch this morning with a roost
of gulls. The gull seems larger-bulkier and has less blue tones than the
nearby Western Gull to it's right. The gull has the smudgy eye and it had some
streaks on the back of the head. There is also a Herring Gull in front of him
for comparison.
There are four pics altogether on Flickr.
PS - I still have a Mountain Chickadee visiting my feeder daily in
Manzanita/Nehalem.
PSS - I had a Rufous Hummingbird on the 23rd and a bird-loving neighbor nearby
says she saw a Rufous Hummingbird in her neighbor's yard a couple weeks before
that!!!
https://flic.kr/p/ECopz6
https://flic.kr/p/ECorsp
https://flic.kr/p/DEEkpL
https://flic.kr/p/EuahAM
Thanks, Beverly Hallberg
