I'm out-of-town and can't completely comment on this thread, but
I can briefly offer why the AOU considers the Northwestern Crow a "good" species, and in fact is the crow occurring in most of western Washington.

There is a long and fascinating history of this species. It
was recognized as valid (by the AOU) from before that body's
inception until the mid-1920's, when they reduced it to a
subspecies of American Crow only to unleash a torrent of scientific
criticism by ornithologists of this region. Therefore, in 1945,
despite widespread lumping of other taxa (orioles, rosy finches,
etc.) at the time, they resplit the NW Crow.

Since then, the ONLY contrary "SCIENTIFIC" evidence (that it should
not be considered a valid species) is Johnson's 1961 paper, and
that paper can easily be shown to be methodologically flawed.
There is considerable other (mostly older, not necessarily
convincing) evidence that it should be split. Thus, the NW Crow
remains a species in much the same way that O.J. Simpson remains
a free man: despite considerable opinion, no truly convincing
evidence ever was offered (to the jury) to the contrary, and the
"null" hypothesis in taxonomy is generally precedence. Criticizing
the jury (in the crow's case, the AOU Check-list Committee) is not
helpful.

This is a great opportunity for a PhD thesis, but no one has undertaken it, unlike the situation with Western-Glaucous-winged Gulls. An excellent paper summarizing D.A. Bell's findings about those taxa was published in Condor in 1996. That paper also gives a good summary of the most currently fashionable concept of a species
in ornithology--i.e., why those gulls both are considered "good" species despite a widespread hybrid zone.

I hope this helps, even if it leaves out a lot of details.

Bill Smith
Grays Harbor
pwsmith at techline.com