Subject: Great Black-backed
Date: Jan 20 17:16:02 2004
From: Eugene and Nancy Hunn - enhunn at comcast.net


Phillip, Ryan, et al.,

We do appreciate the relevance of structure, but we also appreciate that
structural features may vary widely within a species.

With regard to the structural features Phillip mentions as being anomalous:

gonys angle: I've carefully compared the photos in Grant (N = 18) with a
number of the Renton bird and the gonys angle appears indistinguishable to
my eye, in fact, not particularly prominent in any of the birds illustrated.

forehead profile: the "bump" on the Renton bird's forehead is matched by
Grant's 302, 308, and 309, at least, as well as by the bird illustrated on
the website Ryan just posted.

position of eye: I can see no difference.

relative size of head and body: I can see no difference.

"roundness" of body versus flat belly: this appears quite variable depending
on posture, but the "round belly" attributed to the Renton bird is matched
perfectly by Grant's 300.

curvature of culmen tip: This is often hard to make out given the coloration
of the bill tip, but I can see no difference.

primary extension beyond tail: I can see no difference.

If I've missed something, sorry.

I just don't see what you report seeing. That's why I say these features are
subjective. I have some familiarity with the literature on the psychology of
perception and am aware that eye-witness testimony can be notoriously
unreliable, that we tend to see what we expect to see. Only by physically
measuring the features (as ratios, of course, and with careful attention to
the precise method of measurement and holding posture constant) can we
entirely rule out these effects.

Gene Hunn.

----- Original Message -----
From: "Phillip Pickering" <philliplc at harborside.com>
To: "Eugene and Nancy Hunn" <enhunn at comcast.net>;
<tweeters at u.washington.edu>
Sent: Tuesday, January 20, 2004 12:56 PM
Subject: Re: Great Black-backed


> Gene etc,
>
> The anomalies I mention are not subjective. Although this
> gull is so radically off structurally for GBBG that I don't
> find it necessary, things like relative head/body length and
> body width at certain points, and other aspects of shape
> and proportion can certainly be measured in photos and
> compared. I would hope the WBRC would do exactly
> that before accepting this bird as a pure GBBG.
>
> Respectfully, to anyone interested in a completely objective
> approach to this gull I'd recommend spending a few hours
> studying GBBG photos on the web (Google image search
> brings up access to over 150), and specifically comparing
> (try measuring if you want) the aspects I mentioned. Some of
> them such as the difference in culmen downcurve and typical
> head shape should become fairly obvious even if you aren't
> used to looking at such things. The photos in Grant also
> show the shape differences I mention, although for someone
> not intimately familiar with GBBG structure it will take more
> than a glance to see them and compare them to the Renton
> bird.
>
> True I don't have any real life experience with this species. But
> please concider that I have spent the last 5 years doing virtually
> nothing but training myself to identify seabirds by shape and
> proportions, both in the field and in photos. I can say for a fact
> that it's not that hard to pick up on and compare those aspects
> of a species (or individual) from a series of photos if you take the
> time to train yourself to do so.
>
> In any event, as those that subscribe to ID Frontiers are aware
> at least a few of the more prominent and experienced gull enthusiasts
> who have studied GBBG in life share my concerns with the Renton
> gull's structure. They just have the good sense to not be quite
> so obsessive about it.
>
> Cheers,
>
> Phil
>
>
> ----- Original Message -----
> From: "Eugene and Nancy Hunn" <enhunn at comcast.net>
> To: <philliplc at harborside.com>; <tweeters at u.washington.edu>
> Sent: Tuesday, January 20, 2004 11:51 AM
> Subject: Re: Great Black-backed
>
>
> > 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.
>