Subject: [Tweeters] Re: gull talk
Date: Mar 15 12:52:25 2008
From: Dennis Paulson - dennispaulson at comcast.net


Gene Hunn wrote:

All this gull talk has been fun, but Cameron's latest post puzzles
me. If
the Slaty-backed Gull is so distinctive that it can be recognized at a
glance by its "structure" regardless of sex, age, or situation, at
least by
those in the know, what sort of genetic or evolutionary anomaly is
responsible, given that we mere mortals must struggle to sort out the
more
common big gulls around here?

Gene Hunn

------------------

And indeed the fact is that these gulls are obviously very closely
related to one another, if both the frequency of hybridization among
them and the minor genetic (DNA) differences among them are to be
believed. As they don't seem to do such a great job of distinguishing
one another, then why should they be (or look) very different in
structure?

I should add that I can't see many of the differences that have been
pointed out, and I see what looks to me like an infinite variation in
shape when I just look at a bunch of Glaucous-winged Gulls. Within
any large, white-headed gull, I see rounder and flatter heads, longer
and shorter necks, pot bellies and slenderellas, bigger and smaller
bills, fluffier or flatter "skirts," about as much variation in
"structure" as one would expect in a big bird, and it looks like any
two species that are similar in size overlap in these characters. I
agree that there are average differences, but all you have to do is
look at a complete series of photos of any species in Howell & Dunn's
gull book, and you can see the amount of variation that makes these
differences hard to assess in a single bird.

I concede that others may have better eyesight or a more discerning
brain than I do. But if big gulls are so easy to identify, why are
listserves so full of arguments about them?

-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net



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