-----Original Message-----
From: Turaco14 at aol.com
Date: Friday, January 01, 1999 9:07 PM
Subject: Northwestern and American Crows

>Tweeters -
>
>I just have to ask. All the crows I see flying over my house by the
hundreds
>each afternoon are . . .? Are they American or Northwestern? I've been
>entering them into my Birder's Diary as American and if they aren't
American,
>I'd sure like to change what I've entered.
>
>Thanks,
>
>Tyler


I'm sure several more qualified people will answer this, but here's a start.

Almost all the birders I know around here have given up trying to
distinguish American (AC) and Northwestern (NC) Crows because the local
subspecies of American Crow is smaller than most, so that they are
essentially indistinguishable in the field. Also, none of the reported
fieldmarks seem to work reliably:-- good luck trying to separate them by
voice, for example.

So there are essentially three theories:
1) Northwestern and American Crows are not good species, but the crows tend
to be smaller in the far northwest. The barriers of the cascades and the
sound therefore create an illusion of two different types.

2) There are two species with little interbreeding, but the gradual
variation in size in both species makes them extremely difficult to tell
apart in the south east part of northwestern's range (i.e., here).

3) There are two good species, but where they meet (i.e., here) there is a
'hybridization zone' with much interbreeding. This would be very like
Western and Glaucous-winged Gulls in the Puget Sound.

I'd about given up on them until I read Pyle's ('Identification Guide to
North American Birds, Part one') account, recently. This is mostly for
birders who have the birds in hand, but at least he describes the local race
of the American Crow Corvus brachyrhynchos hesperis and reports the
following possible (note: possible!!) distinguishing features (note: you've
also got to age them properly, which I'm not going into here):

1) Adult wing sizes AC ad male 277-330mm AC ad female 272-317mm; NC ad male
268-302, NC ad female 257-289.

2) AC underparts glossier, NC underparts flatter black

3) AC: nasal bristles along the sides of the bill; NC nasal bristles along
the culmen

4) AC juvenile's mouth lining pinker; NC mouth lining more orange

This appeals to me because I've definitely seen variability between the
crows of Seattle and Sequim in glossiness and the extent to which the
primaries extend beyond the tail when the plumage is fresh. Does this mean
that I'll start claiming NC? Nah, but it's interesting, and I might measure
the wings of some roadkill.

All that's a long way of saying that when I see a crow around here,
Bainbridge and points west, I report it as Crow sp. But let's hear what the
experts say...

Nigel Ball
Bainbridge Island
nball001 at msn.com