Hi Tweets,

Disclaimer: Warning, some technical content follows.
I welcome comments or questions to clarify if anyone
needs it. And as always I welcome lively discussion
of the topic below.

Burt brings up some interesting points here, but I
think he oversimplifies the matter quite a bit when he
starts talking about the genetics at the end. Many
people who don't understand what mtDNA is and how
phylogeny reconstruction works often ask about it.
Thus the question "how great a difference in DNA is
necessary to define distinct species?" is an entirely
ignorant one from a scientific view. Aside from not
specifying nuclear and mitochondrial DNA it fails to
address comparison with other closely related species
which does in fact put sequence differences in
perspective. Testing for percent sequence differences
in the DNA of two species tells you NOTHING about
speciation and Burt is correct on this point (it does
tell you the time since divergence and perhaps the
nature of divergences but nothing about whether two
things are actually the same species or separate
species). HOWEVER, large sample studies of
mitochondrial DNA can tell us a great deal about
speciation through phylogeny reconstruction. This is
the point that most people don't really understand.
By comparing the sequences of not only species of
interest but also including closely related groups for
comparison, you can tell whether groups are
monophyletic and reciprocally monophyletic which is
very important for the designation of species. There
was a short piece on this in reference to California
Thrashers in a recent issue of Birding (Sorry, I don't
have the issue in front of me to give the date) which
I think everyone should read if they really want to
understand how this works.

To stray from the subject of the phylogeny of corvids
for an illustration and possible point of future
discussion, recent work with the genus Parula (Auk
118(1):211215, 2001 for the hard copy or at
http://www.eeb.cornell.edu/lovette/pdf/Parula%20relationships.pdf
for the PDF version on the web) has shown that two
species (Crescent-chested Warbler - Parula
superciliosa and Flame-throated Warbler - Parula
gutteralis) are actually more closely related to
members of the genus Vermivora than they are to
Tropical and Northern Parula (Parula pitiayumi and P.
americana respectively). This was suspected by some
ornithologists for a long time, but the mitochondrial
sequences with many other species used as "out groups"
for analysis confirmed this. What I find even more
interesting about this paper, however, is not only
were Tropical and Northern Parula's found to be more
properly placed in the genus Dendroica, but that they
were not reciprocally monophyletic i.e. some Tropical
Parulas from south America (there are 13 subspecies
and not all were sampled) were more closely related to
Northern Parulas than they were to Tropical Parulas
from Central America and Mexico. We may very well see
some lumping and or splitting going on in this group
in the future.


Michael Dossett
Bothell, WA
Phainopepla at yahoo.com



--- "Guttman, Burt" <GuttmanB at evergreen.edu> wrote:

---------------------------------
RE: Northwestern Crows
Once again, the "Northwestern Crow" has raised its
ugly black head for the wonderment and amusement of
all Tweets. And once again we have a bunch of field
observations to support some particular ideas about
the distribution and biology of these little critters.
This issue comes up every year or two. What amazes
me is that no one goes back to the most definitive
study I know of on the matter, David W. Johnston's
1961 book The Biosystematics of American Crows,
published by U.W. Press. Johnston examined the
"Northwestern Crow" question at length. (Let me get
the terminology straight: The American (Common) Crow
is Corvus brachyrhyncos; the "Northwestern Crow" was
named C. caurinus.) He began by carefully studying a
lot of skins from museums; he notes his puzzlement at
finding specimens from the same place apparently
arbitrariily labeled brachyrhyncos or caurinus;
specimens with identical measurements assigned to the
two species; specimens variously labeled as one
species or the other or as hybrids, for no apparent
reason; and specimens whose measurements place them
outside the range of the species they are assigned to.
After all this confusion, he determined that he could
only resolve the issue by doing some extensive field
work of his own. You should read this; I won't try to
copy it all here. But one of his most important
observations was about the voices of crows, which are
supposed to be definitive characteristics of the
species. (See Wayne's notes below where he refers to
voice.) Johnston noted, first, that whereas the
"Northwestern Crow" was supposed to have a voice
similar to that of the Fish Crow (C. ossifragus) of
the southeast, their voices are actually quite
different. But, most important, he observed that
individuals could produce quite different calls at
different times, so at one moment you would want to
call a bird brachyrhyncos and at the next moment
caurinus. Let me quote Johnston's conclusions:

"All the data presented here--voice, habitat
choice, measurements--clearly negate any hypothesis
that crows of northwestern North America represent a
distinct species. Rather, the evidence points to the
existence of a zone of intergradation in southwestern
Washington and restricted localities in British
Columbia where crows from the northern and southern
populations freely interbreed with one another. In
the absence of clear-cut differences between the
northern and southern populations and the absence of
reproductive isolation, it follows that the
Northwestern Crow is simply a well-marked, ecologic
subspecies of C. brachyrhyncos. It is with this
conclusion in mind that the crows of Alaska and
coastal British Columbia should by called C.
brachyrhyncos caurinus, those of Washington west of
the Cascade Range are intermediates, and those of
Oregon, California, interior Washington and British
Columbia, and Idaho, C. b. hesperis."

Finally, Ian notes that someone at the U.W. is
doing some kind of DNA study on crows. Well, fine,
but I wonder what they expect to find. People who
don't understand genetics very well seem to be
entranced with DNA these days; the question came up on
Birdchat recently, where someone asked how great a
difference in DNA is necessary to define distinct
species. The answer, of course, is that the
connection between DNA sequences and the biological
features that make for distinct species (or not) is so
complex and tenuous that the DNA by itself will tell
you essentially nothing. (Natheless, there are
important questions of genetics and evolution that can
be addressed by examining specific features of certain
DNAs--I don't want to imply that such research is
useless.)

Burt Guttman
guttmanb at evergreen.edu
The Evergreen State College
Olympia, WA 98505
360-456-8447
Home: 7334 Holmes Island Road S.E., Olympia 98503


-----Original Message-----
From: Wayne C. Weber [mailto:contopus at telus.net]
Sent: Saturday, April 19, 2003 5:07 AM
To: TWEETERS
Cc: BOB NORTON; IAN PAULSEN
Subject: Re: Northwestern Crows and Siberian Accentors


Tweeters,

Woops-- sorry about the 5 SIBERIAN ACCENTORS I
erroneously reported
from Fort Casey State Park on April 15. Bob was right,
it was a typo--
they were actually EUROPEAN STARLINGS!!

As for Northwestern Crows, Bob is probably correct
that Northwesterns
and Americans are not good species-- they interbreed
over a wide area
in western Washington. However, it is my belief, based
on many years
of birding experience, that crows in San Juan and
Island Counties, as
well as those in western Whatcom and Skagit Counties,
are essentially
Northwesterns, as their size and vocalizations to me
appear identical
to those of the pure Northwesterns I see in BC. The
same probably goes
for those in coastal Clallam County and at least part
of Jefferson
County, although I have far less birding experience
there. I call them
as I
see them (and hear them).

I am copying below a message that I sent to TWEETERS 2
years ago on
crow distribution in Washington. If others have
different impressions
of crow distribution, please let us know!

_________________________________________________________


Ornithologists recognize 2 species of crows in the
Northwest: the
smaller Northwestern Crow, generally found in coastal
areas from
south-central Alaska to the Puget Sound area and the
Olympic
Peninsula, and the American Crow, found in all other
areas. However,
in the last 50 to 100 years, American Crows have
spread westward in
Washington due to the creation of new habitat by the
clearing of
forest. They have apparently interbred with
Northwestern Crows to the
point where, in much of western Washington, it's hard
to say what kind
of crow is present, and many of us just call them
"crows". In fact,
the two species should almost certainly be "lumped",
but the American
Ornithologists' Union, which rules on such matters,
has not made this
decision yet.

In southeastern Alaska and in coastal British
Columbia-- unlike
Washington-- there is little or no overlap and/or
hybridization
between the two crows, and any crow seen west of the
Cascade/Coast
Range crest can safely be called a Northwestern.

In my birding experience in WA, virtually all crows I
see in San Juan
and Island Counties, and in western Whatcom and Skagit
Counties, look
and sound like Northwestern Crows, and I record them
as such. Most
crows in coastal parts of the Olympic Peninsula are
probably
Northwesterns as well.

However, by the time you get south to Snohomish and
King Counties, the
picture becomes much more confused, and it is safer to
just call them
"crow species". Even in eastern parts of Whatcom and
Skagit Counties
(e.g. around Diablo Lake), the crows there look and
sound to me like
American Crows.

Others may have somewhat different impressions of the
local
distribution of crows in WA-- and I'd be interested in
hearing them--
but I believe the overall picture I've drawn is fairly
accurate.

Wayne C. Weber
Kamloops and Delta, BC
contopus at home.com

___________________________________________________

----- Original Message -----
From: Robert Norton <norton36 at olypen.com>
To: <contopus at telus.net>; <tweeters at u.washington.edu>
Sent: Friday, April 18, 2003 9:50 PM
Subject: Re:Northwestern Crows and Siberian Accentors,
was Fort Casey
Census


Wayne and Tweeters,

I understand that crow researchers have not yet
been able to
find any small crows with the correct Northwestern
measurements in the
state
of Washington. They were probably here when the white
man arrived but
widespread clearcutting and farming allowed the
American Crows in
and free interbreeding led to the demise of the
species(?) in the
lower 48. I
understand from the Fraser River north into Alaska
they are "pure"
except there is one place in Alaska that American
Crows have reached
and
there are many intergrades there. If anyone knows more
about this than
I do,
please share on the list. I don't think it is a good
species in the
first
place. Only the gulls can get away with such behavior
and still be
called
separate species.
Sure we have some smaller crows along the coast
and they are
present down the coast thru Oregon and in to at least
northern
California
but they are not Northwestern! Maybe too much salt
stunts a crow's
growth!

I presume that the 5 Siberian Accentors were a
typo as Wayne is
a meticulous and knowledgeable birder.

Bob Norton
Joyce (near Port Angeles), WA
norton36 at olypen.com




__________________________________________________
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