Just wanted to add that after reading Andy's comments I took the
liberty of posting a link to the photos on a forum frequented by many
birders from "across the pond".  Link to the thread is here:
http://www.birdforum.net/showthread.php?t=157201
Consensus at this point seems to be running against YLG, but no
consensus yet about what else it might be--possibly a hybrid.  But if
the bird is seen again, a photo of the open wing should be the goal.

Jim Moore
Rockville, MD

On Fri, Nov 20, 2009 at 1:50 PM, pobrien776 <> wrote:
> Here are some clarifications and cautions from someone who has far more experience with Yellow-legged Gulls than I ever will.  Also note that Marcia Balestri is posting the package to IDFrontiers.  That should produce a flurry of responses.  You can find IDFrontiers at <www.birdingonthe.net>, click on Regional/Specialty.
>
> Paul O'Brien
> Rockville, Mont. Co., MD
>
> Begin forwarded message:
>
> From:   pobrien776 <>
> Subject:    Re: [MDOSPREY] Adult Yellow-legged Gull
> Date:   November 20, 2009 12:48:04 PM EST
> To: "Andy Wilson" <>
> Andy,
> I share your cautions.  The mirrors threw me off until I looked at Howell and Dunn, particularly figure 26.1, which shows a good sized mirror as well as extensive fine streaking.  I, too, thought of incomplete molt when I saw the primary extension.  I have no solution for that question, which is one of the reason's I wanted to get more birders, particularly the ones with the gigantic cameras, looking for and documenting this bird.  Flight photos would help on the primary molt question, and on subspecies too.  The size should approach Herring Gull.  I should never have thrown Ring-billed Gull into the equation.  We learn by errors.
>
> Paul O'Brien
> Rockville, Mont. Co., MD
>
> On Nov 20, 2009, at 7:55:51 AM, "Andy Wilson" <> wrote:
>
> From:   "Andy Wilson" <>
> Subject:    Re: [MDOSPREY] Adult Yellow-legged Gull
> Date:   November 20, 2009 7:55:51 AM EST
> To: 
> Thanks for posting the photo link Paul - an interesting bird. While it has lots
> of good value for a Yellow-legged Gull, there are a few things that allow some
> room for uncertainty in my opinion. I'd like to hear the opinion of others with
> experience of this species.
>
> My main concern is the size of the white mirrors on the primaries - they should
> be small on Yellow-legged, they look large on this bird, certainly larger than
> is typical for Yellow-legged. Some of that could be an artifact of the
> photographs - difficult to say. Also, Yellow-legged has longer primaries than
> Herring - this bird has a very short primary projection. Of course that could
> be moult, but note that Yellow-legged Gull (at least the western European race)
> moults earlier than Herring Gull, and I would have thought would be through
> moult by now. I'm not too sure of the moult timing of other races though - so
> that's worth investigating.
>
> Also, the streaking on the head is definitely towards the extensive extreme for
> Yellow-legged Gull. In photo 6 - the streaking looks extensive but very fine.
> Size is difficult to judge but Yellow-legged is pretty close to average Herring
> Gull size, there is extensive overlap among the various races of both. It's
> usually noticeably larger than Lesser-Black-backed (when side by side), a
> Yellow-legged between Ring-billed and Herring size would be odd.
>
> I don't think any one thing rules out Yellow-legged but it's certainly doesn't
> look like a classic bird of the races I'm used to seeing in Europe and North
> Africa. This species complex is, well, complex though!
>
> A good find whatever the outcome.
>
> Andy Wilson,
> Frederick
>
>
> <A name=1258667211>Subject: Adult Yellow-legged Gull</A>
> From: pobrien776 <pobrien776 AT AOL.COM>
> Date: Thu, 19 Nov 2009 16:46:34 -0500
> For those of you who may be in the vicinity of Blackwater Refuge this weekend,
> be on the lookout for this gull. �It was seen last Friday (the 13th!) by
> Marcia
> Balestri, but not relocated over the weekend. �It was with a flock of mostly
> Laughing and Ring-billed Gulls foraging in the fields along Egypt Road north of
> Key Wallace. �For all we know it could be in North Carolina by now, but it is
> certainly worth looking for. �It will be slightly darker in the mantle and
> midway in size between Herring and Ring-billed Gulls, but with yellow legs.
> �Many of you probably missed the 1993 bird at the Oaks Landfill in
> Laytonsville, Montgomery Co. �It shuttled between the landfill and Georgetown
> Reservoir. �It was a return of the first documented North American record
> which
> had been found by Dave Czaplak at Georgetown in the winter of 1990-1991, as I
> recall.
>
>
> Photos can be seen at:
>
> http://picasaweb.google.com/BobsShots/Gulls
>
> Good luck!
>
> Paul O'Brien
> Rockville, Mont. Co., MD
> Eared Grebe - Piscataway Park PG Cty</a> [Joe Hanfman ]
> -->
>