Well, according to my copy of Pyle,et.al. (have they come out with a revision
since 1987?):"The separation is based mainly on differences in vocalization
and habitat. No definitive, in-hand separating criteria are now known,
although coastal forms (Pacific-slope), on average, shorter wings and
narrower bills than interior forms (Cordilleran)."

The U.S. Fish & Wildlife banding manual still refers to them as "Western
Flycatcher" because no criteria acceptable to them has been established
(generally speaking they like 95% certainty on their mensural criteria).

This is a pair of sibling species that may, infact, be so close to the
definitional boundary that it may only be two separate species during the
breeding season (as hard as that is for bird watchers to imagine). This
is a doctoral thesis just waiting for some young energetic ornithologist
willing to radio tag flycatchers and follow them to the winter grounds.

The bottom line... there are jizzy differences that would probably allow
an experienced bander to separate the two "species" in hand. But they are
unlikely to be accepted by the banding laboratory.

>
>On Mon, 13 May 1996 00:01:06 PDT, tweeters at u.washington.edu wrote:
>
>>And (the best for last) a Western Flycatcher 'Pacific-slope' and a Western
>>Flycatcher 'Cordilleran' caught in the same net at the same time on Saturday
>>at the famous Douglas Creek Banding Station. The brit ringer there to observe
>>was thanking his lucky stars there were no Empids in England. You may be asking
>>how I knew the difference in hand. It takes a while, Pyle et.al.,and some
>>experience.
>
><cut>
>
>All right, I give. Just how do you tell the two apart in the hand without
>hearing them sing??????
>
> - Jack
>
>***************************
>*Jack Bowling *
>*Prince George, BC *
>*jcbowling at mindlink.bc.ca *
>***************************
>
>
>

--
*********************************** I was of three minds
* Mike Patterson, Astoria, OR * like a tree
* mpatters at orednet.org * in which there are three blackbirds.
*http://www.pacifier.com/~mpatters* -Wallace Stevens