Doug and Tweeters,

One fact that should be pointed out is that iris color in gulls tends
to be far more variable than the colors of bills, legs, or plumage.
So if the Moses Lake bird fits the description of Lesser Black-backed
in all respects other than iris color, the overwhelming probability is
that it's a Lesser Black-back, especially as Olsen & Larsson note
that a 3rd year bird can have a dark or darkish iris.

Trying to turn this bird into a Heuglin's Gull, or some other species
or subspecies of gull that has never been seen in the western
US, would be a real stretch.

I'm sure that Lesser Black-backed is still on the Review List for the
Washington Bird Records Committee, and I'd be very surprised if they
did not accept this record.

Wayne C. Weber
Delta, BC
contopus at telus.net





----- Original Message -----
From: "Doug Schonewald" <dschone8 at donobi.net>
To: <tweeters at u.washington.edu>
Sent: Wednesday, April 04, 2007 6:23 AM
Subject: [Tweeters] re: Moses Lake Lesser Black-backed Gull (LBBG) -
looooong


Ryan,

Since I found the original bird I suppose I should respond to this bird and
the questions that it has raised.
First let's review what we know about the most likely candidates (that are
not LBBG or are a sub-species of LBBG that would be extremely unusual) that
have been put forth as possibilities for the Moses Lake bird.
'Baltic Gull'- actually a sub-species of LBBG with a Latin moniker of Larus
fuscus fuscus. Migration patterns make this a highly unlikely possibility.
In addition to migrating away from the west coast of the North American
Continent, this bird is in serious decline with less than 20,00, pairs
worldwide (and that population centered in eastern Europe). The biggest
problem with this possibility is that fuscus is a 3-year gull. The Moses
Lake bird is in it's 3rd year and is still not mature. This makes the Moses
Lake bird a 4-year gull and eliminates fuscus as a possibility (though how
in the heck a 3-cycle bird can be considered a sub-species of a 4-cycle bird
is a little beyond my feeble skills).
Heuglin's Gull is the next best possibility. Larus heuglini heuglini,
Heuglin's also migrates away from the western coast of North America and has
no precedent of vagrancy to the west coast of North America. In addition,
most authorities note that Heuglin's molts into summer plumage quite late in
the spring. The Moses Lake bird had almost completely molted into summer
plumage in mid-March when it was located. This is attested to in Ryan's
excellent photos. Another mark against Heuglin's nominate. Also, Olsen and
Larsson note that the nominate race is a 3-year gull (though they contradict
themselves several times on this). L.h. taimyrensis (sometimes considered a
ssp. of Heuglin's) has a migration pattern that might bring it to the west
coast of North America, but there is no precedent for such vagrancy in this
bird either. Taimyrensis is also the palest of the birds discussed thus far,
and should be eliminated on basis of mantle color alone. Taimyrensis is now
considered a clinal hybrid of L.h. heuglini and Vega.
Vega Gull is a possibility, but the Moses Lake bird is way too dark to be a
Vega Gull. In fact I could not find a photo of a pure Vega Gull that was
anywhere near as dark as the Moses Lake bird.
Yellow-legged Gull was considered for a bit (very wishful thinking) but was
almost immediately scrapped based on cycle count (YLGU is a 3-year gull) and
absolute lack of vagrancy pattern to the west or for that matter inland
waters.
That leaves us with some kind of hybrid, or the bird is indeed a LBBG. As
Ryan noted the bird looks good in every respect for LBBG. My feeling at the
time of observation was that "If it looks like a LBBG then it probably is a
LBBG". I did try to make it something else but could not. There is no
indication of a hybrid and that brings us to the eye and location of the
observation. Since we are certain that this is a 3-year bird (and this bird
has a 4-year cycle) I checked Olsen/Larsson and noted that in 3rd year birds
the iris is listed as "often darker, in small minority all dark". This fits
well. Further, vagrancy patterns show that the arrival of the Moses Lake
bird follows vagrancy patterns as LBBG moves across the lower 48 from east
to west.
Synopsis: The Moses Lake gull is a bird with a 4-year cycle that fits all
aspects of color, vagrancy pattern, and molt. LBBG also shows a marked
propensity to return to imprinted locations year after year (a good example
is the LBBG of the upper Grand Coulee lakes and the bird that showed for
several consecutive years on the Walla Walla Delta area). Granted this is
not a 100% certain ID, but for me, 99% certain is pretty good and I'll buy
that any day with gulls.
I do have photos of last years bird. They are not great quality, but good
enough for review and comparison, but I do not have a site to post them (I
keep thinking I'll get this done, but haven't yet). I can send them to those
who are interested.

Cheers

Doug Schonewald
Moses Lake, WA