Subject: Re: CROW TAXONOMY QUESTION
Date: Mar 02 08:40:15 1994
From: Jerry Tangren - GSW$EN at WSUVM1.CSC.WSU.EDU

Dennis Paulson <dpaulson at ups.edu> writes

> I'm startled that Jerry Tangren can so easily tell breeding from wintering
> crows by size. According to Johnston's monograph, in adult males north of
> King Co. vs. those from the interior, wing length differs by 20 mm, tail
> length by 8 mm, tarsus length by 6 mm, and bill length by <1 mm. In all
> cases, the measurements overlap, and these are of course average
> differences. First, I don't think I could distinguish birds by size with
> differences of that magnitude (Johnston recorded average weight differences
> of 8%, with huge overlap), and second, this implies that "Northwestern"
> crows have moved all the way across the Cascades and displaced "American"
> crows as breeders in the Wenatchee area, but that somewhere nearby there is
> a population of "American" crows that move in in the winter. This is really
> interesting news but I think needs documenting. I would love to be shown to
> be wrong and in fact find out that the situation is more interesting than
> we thought. Get people to save road-killed crows, Jerry, and let's measure
> them! Record the voices of the breeding and wintering birds--Gene Hunn
> would be quite interested in examining the recordings, I imagine.
>

Dennis I don't believe you fully understood the meaning and intent behind
my note. My feeling is that as long as the AOU, ABA and other associates
continue to recognise NW Crow as a species, then crows with strong
relationships to the pure NW Crow of the Pacific Northwest Coast might
possibly also be countable on lists et al. as NW Crows. That they are
considered two species is a joke we might as well enjoy.

Here in Wenatchee we do get some larger crows in winter (larger than the
breeding crows). I assume they come from breeding populations well north
of us in Canada. I do not believe they are breeding birds from anywhere
within the state of Washington. However, they are more defintely American
Crows than are our breeding birds. With fingers crossed, tongue in
cheek, and no one saying I can't do it, I am saying that the differences
between these two groups allows me to tally both NW Crow and American Crows
for Chelan Co.

As far as NW Crows crossing the Cascades, that's not so unbelieveable. The
Cascades are not so much a barrier to birds moving east as the sagebrush desert
to the east of the Cascades is. The Cascades themselves are not that high, and
several birds with affinities to the west side of the state find suitable
habitat on the east slope of the Cascades. Take the I-90 corridor between
Seattle and Ellensburg. Crows are continuous along the complete stretch.
The Wenatchee area is on the edge of the east slopes and so is not all that
isolated from the west side populations of birds. I would be very surprised
if Wenatchee breeding crows did not carry some genes from the NW Crow
populations.

As to the status of birds in western Washington, that is a completely
different question. If I had data, I would publish it. But here again my
FEELING is that the situation is probably changing (or has changed) quite
rapidly. Once the NW Crow was isolated from the American, but we are now
seeing a mixing of genes between the populations with perhaps a rather
broad cline now in place. Populations showing intergradation of the NW Crow
may well extent south to northern Caifornia.

What do the Oregon birders think?

Much of the story behind the NC Crow may well be related to the urbanization
of the Pacific Northwest. There is a lot of thought that NW Crows might
make better urban birds than the western races of the American Crow (mere
speculation). Their behavior is well adapted to opportunistic feeding.
Changes even since Johnston did his study could make an excellent case
study.

From: Jerry Tangren, Wenatchee WA
<gsw$en at wsuvm1.csc.wsu.edu>