Jerry Tangren wrote:
2.) Who said the NW Crow needed to develop in isolation? If there is in
fact a cline that extends along the coast from Alaska to southern Calif.,
then any such isolating mechanism is unncessary. True? I'm asking.

There really isn't a cline in crow size from Alaska to California. Birds
from Alaska and BC are all about the same size, but then a rather rapid
cline occurs from southern BC to Oregon, basically through Washington. This
is where we are assuming populations of Am Crow and NW Crow are
interbreeding after a period of isolation. Crows in California are actually
smaller than those in Oregon, so the cline if anything reverses at some
point. Crows in interior BC and WA are about the size of those in OR, so we
assume Oregon crows are bona fide "American Crows." Interestingly, some
individual crows in interior BC and WA are smaller than the smallest OR
crows, perhaps indicating NW Crows crossing the Cascades, as was previously
discussed (not an unlikely event, actually; as Jerry Tangren wrote
previously, crow habitat is more continuous across the Cascades than it is
between crow populations in far eastern WA and those of the Central WA
Cascades. Crows are in the process of colonizing the Columbia Basin right
now, and it would be really interesting to save any road kills in decent
shape that are found in that area.

Dennis Paulson, University of Puget Sound