Subject: Fwd: Renton GBBG comment, ID-F response
Date: Feb 2 18:27:39 2004
From: Scott Atkinson - scottratkinson at hotmail.com
Tweeters:
On the (great) Great BB Gull polemic, like Phillip, I have not gone to see
the Renton gull. In my case, this is in part because I lived in MD for six
years and in trips to the MD-VA coast and saw many GBB Gulls. I also recall
that the species did (especially in winter) wander well inland, sometimes
the Triadelphia CBC in MD, for example, would get one or two.
To reiterate a point made by others: (1) GBB Gull is a wide-ranging
species found in significant numbers, exhibiting at least some variation in
field characteristics. Also, (2) the possibility of a specific hybrid has
never been even close to satisfactorily substantiated by the hybrid school.
For example--where does the interbreeding Glaucous/GBB Gull population (or
other hybridizing pair) population occur? Last time I checked, there was no
documented zone of breeding overlap for Glaucous and GBB, but perhaps I am
mistaken and there is more up-to-date information....If Phillip or one of
the others saying potential hybrid could make a compelling argument for
which hybrid they believed the bird was, that would make for a stronger
case. Further--have any of these hybrids been documented as occurring in
the West elsewhere? That would be good to know, because as it stands now, I
have not heard of any, whereas wandering GBB Gulls have been found several
times, as others noted, making them more likely.
Even if there is a zone of breeding overlap that I missed, I find myself
thinking that in terms of numeric probability, the chance of a hybrid
Glaucous x GBB showing up in WA, versus that of a GBB, is exceedingly
small--the number of "pure" GBBs must be (almost) infinitely greater than
that of GBB x Glaucous hybrids...Also, I'm not so sure about the "wandering
hybrid" argument--seems more likely that a GBB x Glaucous hybrid (if they
are out there) would be more likely where both parents are known to occur,
say, somewhere like the northeast coast. Yet I don't recall any of the CBCs
out there reporting any. I also observe here that Phillip notes that
Leukering, who he cited in his case for hybrid, said that integrades "may
potentially wander" more than adults--a very tentative argument (may,
potentially) by choice of words....The hybrid gulls I've encountered more
than once, like GW X Western, GW X Glaucous, the Herring hybrids, were in
places where both parents had been documented as occurring at least
annually, although hybrids can reach a new area before "pure" birds, too.
Finally, as impressive as the photo data base has been, there is no
substitute for in-the-field observation. My case is weakened by not having
been there. Yet (again, unless I've missed something), not one of the field
observers (which includes present/past members of the WRBC, hardly known
historically for lax policy in accepting new state records, as Phillip
implies is happening now), has come back and said they think the bird might
be a hybrid. 300 photos/200 birds is a good count; but how many GBB gulls
are out there now, and how many have come and gone? 300 seems a paltry
figure when this is taken into account, and again, as useful as photos are,
they are not the complete data base on this bird. This is further
underscored by the fact that different observers are drawing different
conclusions from the same photos! No wonder there are more field guides
with illustrations than photos.
"for some in Washington, the tendency might be to give more weight to the
positive and be less
attentive of the negative, when in the case of a potential first state
record such as this the exact opposite should be true"--one could state just
the opposite, that, for some out of Washington, the tendency might be to
give more weight to the negative, and be less attentive to the positive. As
far as the notion that it should be disconcerting that the bird is
questioned by some, I can't speak for others but can for myself: this is
not disconcerting. Any rarity showing up under these circumstances would
create controversy, invariably there will be proponents as well as
naysayers.
Therefore Phillip's use of the word disconcerting could bely his own
feelings, given that it would be very disconcerting to me if those who had
seen the bird in the field (including those with previous GBB experience on
the WRBC) have come back saying GBB, whereas I stand in a small minority
saying likely hybrid, without making a case for which, and--why else would
Phillip go to so much trouble to attempt policing any reports of GBB on
Tweeters with long treatises like these, when he could do it off-line and
spare us all the tireless repetition of his arguments?
Scott Atkinson
Lake Stevens
mail to: scottratkinson at hotmail.com
>From: "Phillip Pickering" <philliplc at harborside.com>
>Reply-To: philliplc at harborside.com
>To: <tweeters at u.washington.edu>
>Subject: Fwd: Renton GBBG comment, ID-F response
>Date: Mon, 2 Feb 2004 14:56:22 -0800
>
> > Structurally it's prefect, and I see
> > nothing to suggest it's any type of hybrid.
>
>
>My opinion aside, if that were true why would some of those
>who are intimately familiar with GBBG have expressed such a low
>comfort level with the structure? (both on the list and in personal
>comm.) If it were structurally perfect that wouldn't happen, at
>least not to anywhere near the extent it has. The series of photos is
>excellent, and there's no reason to suspect that they are misleading
>anyone.
>
>I bring this up (again, sorry) to amplify the point that there are
>both multiple positive and negative opinions out there about
>this bird - and it seems that, at least for some in Washington, the
>tendency might be to give more weight to the positive and be less
>attentive of the negative, when in the case of a potential first state
>record such as this the exact opposite should be true. Even if you
>don't agree with them, the fact that others who are familiar with
>GBBG are questioning it at all should be disconcerting for such an
>extralimital bird, particularly if you take seriously Tony Leukering's
>argument about intergrades potentially being more prone to
>wander out of range than pure birds.
>
>As for myself, in extensive photo study (pushing 300 photos of well
>over 200 birds) I have not been able to find a GBBG that shows a
>structure similar to the Washington bird. Compared to their body bulk
>GBBG seem to invariably have proportionately larger heads, eyes, and
>bills, seem to almost invariably be more attenuated in the rear and have
>much flatter bellies, and seem to almost invariably have a steeper, less
>gradual culmen downcurve. If 200+ birds can be considered an
>adequate sample, at the fine level necessary to confirm it IMO as
>a whole the bird does not appear to be within the normal structural
>range of variation of pure GBBG *at all*. The structure is that odd.
>As Alvaro said, it doesn't really fit anything, which for me sounds a
>fire alarm that, even though the patterning is close to GBBG, there
>is still a very high probability of it being an intergrade.
>
>Respectfully,
>
>Phil Pickering
>Lincoln City, Oregon
>philliplc at harborside.com
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