I cast no aspersions on people's ability to determine size of birds in the field, but I should point out that from the study of specimens, there is a steady increase in crow size from the BC coast to Oregon in one direction and into the interior of Washington in another direction. There is no sudden change in size. We have a lot of crow specimens from different parts of Washington in the Slater Museum, and they all look about the same size to me. The average wing chord differs by 2 cm between nw WA and the interior of the state, but with a huge amount of overlap. Tail length in these populations differs by < 1cm, tarsus by 3 mm, bill by 1 mm. These are very small differences.

Thus I think there should be no place with "bigger" and "smaller" crows, although I have heard people claim for years that they can distinguish two size classes. I wonder if the power of suggestion is at work. Maybe in Bob's yard . . ..

David W. Johnston, in his "Biosystematics of American Crows" (1961), spent 11 pages discussing "the Northwestern Crow problem." He felt that all the evidence he was able to gather pointed to the lack of specific distinctness of the NW Crow. It could be recognized as a subspecies, with a substantial zone of intergradation with "Western" Crows. I still don't know why the AOU Checklist Committee continues to maintain it as a separate species.

Dennis Paulson
Seattle


On Jun 21, 2012, at 12:00 PM, tweeters-request at mailman1.u.washington.edu wrote:

> Date: Wed, 20 Jun 2012 18:13:59 -0700
> From: "Mike M" <strix-nebulosa at centurylink.net>
> Subject: Re: [Tweeters] Northwestern Crows
> To: "Tweeters" <tweeters at u.washington.edu>
> Message-ID: <C8575253596246BB944EAC4F7F74BC16 at Mikedesktop>
> Content-Type: text/plain; charset="windows-1252"
>
> Bob,
>
> I worked on the Olympic Peninsula for 3 years in the 1990s and my experience was similar to what you are describing. On the west side there was a very distinct line only a few miles inland. For example the crows at Mora or Ruby Beach in the park were noticeably smaller and had distinct vocalizations from those east of Forks. Although it was rare a couple of times I did have an interior (American) crow show up on the beach where it?s larger size and different vocalizations would make it stand out. I don?t ever recall seeing a northwestern type east of US 101. In my experience the two crow types pretty much keep to themselves with very little mixing.
>
> As for diet I suspect that both crows are simply taken advantage of what nutrients are available. For example when I was living in Skagway, AK where American Crows are generally not considered to occur the northwesterns were quite happy dumpster diving and feeding on roadkill or bear kill.
>
> Mike Munts
> Colville
>
> From: Bob and Barb Boekelheide
> Sent: Wednesday, June 20, 2012 5:51 PM
> To: Gene Hunn ; Tweeters Tweeters
> Subject: RE: [Tweeters] Northwestern Crows
>
> Look no further! The zone of contact is clearly my yard in Dungeness, WA. I look north and west, the crows sound dark and woodsy, their vocalizations end with "aye," and they eat clams and shore crabs in Dungeness Bay. I look south and east, the crows sound kind of corny, their vocalizations end with "aw," and they eat my walnuts, roadkill, and baby birds (which of course they "farm" for optimum energy consumption!). Once again science proves the obvious.
>
> Since we have lovely Olympic Gulls here with befuddled parentage and sympatry, how about if we just call all the crows in western Washington "Olympic Crows." Have you heard the S'Klallam story about how "Crow" was hanging out with a bunch of large pink-legged gulls in the intertidal one day, and, before you know it, Crow couldn't tell who he was, either?
>
> Bob Boekelheide
> Dungeness



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