[obol] Slate-colored or cismontanus junco?

[Cameron Cox]

Greetings,

Greg Gillson brings up one of my favorite subjects, field identifiable forms 
of juncos.  Since I have a tendency to go on at length, if junco 
identification is not your thing, save 10 minutes of your life and delete 
now.

First, what is cismontanus?  It is currently recognized as one of three 
subspecies that make up the Slate-colored Junco, designated by the 
scientific name Junco hymalis cismontanus.  However many authorities believe 
that cismontanus is better defined as an intergrade between the 
Slate-colored and Oregon Junco, not a subspecies.  Whatever the true 
taxonomic status of cismontanus, it is convenient to think of them as 
intermediates between the Slate-colored and the Oregon groups of 
Slate-colored Junco since this is what they resemble.  They breed in the 
Canadian Rockies, and are also known by the name Cassiar Junco.  Sibley has 
an excellent illustration of an adult male that he calls the Canadian Rocky 
Mountains variant.  Beadle treats them as an intergrade in one of his 
sparrow books and as a subspecies of Slate-colored in the photographic 
sparrow guide. I have no idea what the status of cismontanus is in Oregon, 
however in western Washington they are regular in very small numbers.  I 
have never seen more than five in one day and they are usually slightly 
outnumbered by true Slate-colored Juncos.

With a rough definition out of the way, is the junco on Greg’s site 
cismontanus?

http://thebirdguide.com/temp_images/RecentPhotos/RecentBirdPhotos.htm

It would be nice to have a couple more photos, particularly one with a good 
side profile, but from the current photo, I would not call this bird 
cismontanus.  It appears to be a Slate-colored Junco, which often have a 
brown wash on the back.  The break between white and gray on the breast is 
clearly concave, while most cismontanus have a convex division.  Typical 
cismontanus would have a slightly darker head and a fairly well defined 
Oregon junco-like hooded impression.  Also the bird in the photo has the 
blueish gray head and breast more typical of Slate-colored.  The head and 
breast of cismontanus looks colder, lacking blue tones. It does appear to be 
a Slate-colored, but I don’t believe it is a female.  To me it suggests a 
first-cycle (1st year) male.  First-cycle females tend to be much paler, 
washed out and are often quite brown or tan.  Adult females can be quite 
similar to this bird but are paler gray with less extensive gray flanks and 
usually lack the darker lores shown by males.  Also you can see that this 
bird has broad brown edges to the tertails, more typical of first-cycle 
Slate-colored of both sexes though some adult females do show them.  
Hopefully some will find this interesting.

Good Juncoing,

Cameron Cox

Seattle, WA

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