The rictal bristle "field mark" was mentioned, I believe, in some bird
banders handbook. We field tested it when we learned of it but found it
to be unreliable. Likewise unreliable on museum skins. An exchange on
this topic was published in WOS Notes by Ian Paulsen et al. As for the
number of transverse muscles across the syrinx. What is the sample
size? Are crow vocalizations so discretely two-valued? They seem to
have quite a range of vocalizations to my ear, including pitch, quality,
and pattern.

Gene Hunn.

On Thu, 29 Jun 1995, Michael Price wrote:

> Hi Tweets,
>
> I heard somewhere (don't remember where) that there are only two significant
> differences between Northwestern Crow (NOCR) and American Crow (AMCR): one
> is anatomical, that NOCR has 4 bands of transverse muscle across its syrinx
> where AMCR has only 3, hence its deeper voice; the other, that rictal
> feathering is species-diagnostically different.
>
> Anyone know yea or nay to these things?
>
> Michael Price
> Vancouver BC Canada
> michael_price at mindlink.bc.ca
>
>