Phillip,

With all due respect, I've reviewed one again the photos of the Renton bird
and those in Grant (which is what I have available to me) and just don't see
what you are seeing. If you can find a way to quantify your subjective
impressions (and that's what they seem to me to be), I'll be happy to
consider your points. I'm sure you've spent a lot of time studying gull
photos, but we've spent many years (nearly 40 in my case) closely examining
all variety of local gulls, as well as those somewhat further afield. On the
basis of my experience I can't accept your analysis.

Gene Hunn.

----- Original Message -----
From: "Phillip Pickering" <philliplc at harborside.com>
To: <tweeters at u.washington.edu>
Sent: Tuesday, January 20, 2004 11:22 AM
Subject: Re: Great Black-backed


> Washington Birders,
>
> Just wanted to summarize in this forum the concerns that many
> of you already know I have about the Renton gull.
>
> While the Renton bird is very much like a GBBG in plumage
> patterning, I feel very strongly that there is something wrong with
> its structure for that species. Structural aspects are every bit
> as vital as plumage for supporting such an extralimital large gull
> as this, and although Washington birders have done an excellent
> job with plumage analysis, I respectfully suggest that the bird's
> structure isn't being scrutinized at the necessary level of detail.
> Yes it's a large bird, easily within the range of bulk of GBBG,
> but that in itself is not enough. Different species of gulls vary not
> only in size, but also consistently in certain aspects of shape, so
> shape is absolutely critical to ID support in a case such as this.
>
> These shape aspects can be subtle (although some can be fairly
> obvious), and might require a good deal of experience with a
> species to get a feel for. Due to my relative inexperience with
> that species, when the first series of photos were posted I
> thought the Renton bird appeared to be shaped reasonably
> similar to what is typical for GBBG (other than the bill), but as I've
> studied numerous GBBG photos it has become more and more
> clear to me that this bird has multiple specific structural features
> that seem at best borderline for that species, and as a whole
> they seem likely to be completely outside GBBG's apparent
> normal range of variation. These structural anomalies are
> consistently evident in every photo that has been posted, and
> they are largely independant of changes in appearance due to
> posture. In most cases they are also independant of male/female
> variation -
>
> - head shape is strange for GBBG. Although some females
> can have fairly rounded heads, the vast majority of GBBG
> show a flatter forehead lacking such a pronounced angle out
> in front of the eye, and show a shallower forehead/bill angle.
> - perhaps due to the atypical head shape, the eye placement is
> somewhat centralized in the face, while on a typical GBBG the
> eye appears slightly higher and/or closer to the forehead.
> - body shape is very strange for GBBG. The vast majority
> including both male and female do not show such a rounded
> look, having flatter bellies and a more attenuated rear end in
> all postures. On average they also show a bit longer primary
> projection beyond the tail, although that feature is somewhat
> more subtle and more subject to photo angle.
> - proportions are radically off. The Renton gull's head, eye, and
> bill are actually proportionately quite small compared to its body
> size for any species that I can think of, and exceptionally so for
> GBBG, which is probably proportionately the largest headed of
> all North American gulls. This takes practice to see, but after
> looking at it in many photos it's fairly obvious to me, so obvious
> in fact that I suspect it's something that could be measured and
> compared in photos. Since the URL to photos of the accepted
> Idaho GBBG is below, look at the proportionate head and
> bill size of that bird to its body compared to the Renton bird.
> The two birds are about as radically different in head/body
> proportion as any two large gulls can be. In my experience,
> misproportioned head and body is a relatively common
> feature of more obvious large gull hybrids.
> - as far as bill shapes vary, the Renton gull's bill is shaped quite
> different than the vast majority of GBBG. GBBG have thicker
> bills, typically with a more concave edge to the lower mandible
> and more gonydeal angle. The Renton gull's bill is remarkably
> straight for that species. Also, I am unable to find any photos
> of GBBG with such a long, gentle downslope to the culmen
> end. GBBG typically show a much steeper, sharper downslope,
> and a blunter look to the bill.
>
> Given how well the plumage patterning seems to match 2nd-
> winter GBBG, I must concede that there is a very good
> chance it is part, perhaps largest part that species. However,
> my opinion based on a lot of my life wasted over the last
> several years studying gull structure and how it varies among
> individuals of a given species, and hybrids, is that this bird
> is very unlikley to be a pure GBBG. I'd also suggest that
> this bird's size alone doesn't necessarily preclude crosses
> not involving GBBG. Occasionally more obvious large gull
> crosses will exhibit features seemingly not matching either
> parent or what a mix of the two would be logically thought
> to produce. And, although this gull's body is huge, it's head
> and bill in comparison to the other species in the photos don't
> appear to be outside the normal range of Glaucous (can't
> necessarily be assumed it would be a barrovianus cross).
> It of course could be argued that the size combined with
> plumage patterning makes non-GBBG crosses unlikely,
> but that's a separate issue.
>
> Perhaps the bird will stick around long enough to molt further
> into 3rd-summer plumage, which should be quite telling.
>
> Cheers and good gulling,
>
> Phil Pickering
> Lincoln City, Oregon
> philliplc at harborside.com
>
>
> >Seriously though, I was able to view it at ca. 100 feet this morning
> (Monday,
> Jan 19) between 11:30 AM and noon standing on a log boom at the north end
of
> Gene Coulon Park in nice sun. I can see no reason to think it's anything
but
> a
> perfectly good example of a 2nd winter Great Black-backed Gull, with a
bill
> that is a bit advanced, cf. 2nd summer. Nothing unusual about that. It's
not
> huge but well within the range of a Great Black-backed in size. In
> particular,
> every plumage detail seems to match the photo in Grant of a 2nd winter
bird
> with the greater coverts a bit more worn (figure 301, pg. 277, a November
> bird)
> with the bill transitional to the photos of 2nd summer birds (figures
> 302,303,304). The white spot near the tip of the outer primary is shown in
> Grant's figure 304 for a 2nd summer bird.
>
>
> Sibley's illustration of a 2nd winter bird standing is a dead ringer,
> including
> the bill coloring and the P10 spot, though perhaps too clean gray on the
> scapular ground color.
>
>
> The Idaho record from last December (2003) is clearly of a different bird,
> in
> 1st winter (cf. www.octoberweb.com/birds/gbbg).
>
>
> Gene Hunn.
>