Subject: Northwestern Crows
Date: Apr 23 12:21:44 2003
From: Robert Norton - norton36 at olypen.com


RE: Northwestern Crows Thanks to all that have spoken on the subject. Particularly to Burt since I did not know of the Johnston work on the subject.
The one thing not mentioned in Burt's coverage is the subject of the calls of immature crows which I (and I suspect others) find hard to differentiate from Northwestern Crows. I also have heard individuals that will give a Northwestern type call and later will give an American type call.
It has all been helpful to me and, I hope others. Bill Tweit told me once that he found all white birds and all black birds to present the most difficult problems in field identification. Coming from Arizona where telling the difference between crows, and two types of ravens was a field problem that always perplexed, I was amused when to make a point in an article on the most common misidentification problems that visiting birders to Arizona have, Gary Rosenberg said, tongue in cheek, that the only Chihuahuan Ravens that can be identified are in the parking lot of the Denny's in Sierra Vista.
..
Bob Norton
Joyce (near Port Angeles), WA
norton36 at olypen.com
----- Original Message -----
From: Guttman, Burt
To: 'contopus at telus.net' ; TWEETERS
Cc: BOB NORTON ; IAN PAULSEN
Sent: Wednesday, April 23, 2003 9:22 AM
Subject: 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