274 THE CHICKADEE. 
General Range.—E astern North America north of the Potomac and Ohio 
Valleys. “A separate ‘colony’ inhabits the area between the Rocky Mountains 
and the Cascade Range, in eastern Washington (Walla Walla, Ellensburg, etc.), 
western Idaho (Lemi, Fort Sherman, etc.), and central British Columbia (Sica- 
mores [Sicamoos], Clinton, Ashcroft, etc. ).2”—Ridgway. 
Range in Washington.—As above. 
Authorities.—P. a. occidentalis. Brewster, B. N. O. C. VII. 1882, 228 
(Walla Walla). J. If this colony proves to be completely isolated, as claimed, 
the bird should, perhaps, be separately named, and I would suggest Penthestes 
atricapillus fortuitus. 
Specimens.—B. P'. 
THE Chickadees of eastern Washington, east of the Cascade foothills, 
along with those of northeastern Oregon, western Idaho, and southwestern 
British Columbia, are notably larger and brighter than P. a. occidentalis. 
In these and other regards they exactly reproduce the characters of P. 
atricapillus, which is a bird of the eastern United States, and from which 
they are widely separated by P. a. septentrionalis. Now Chickadees are 
resident wherever found. ‘The most severe winters do not suffice to drive 
them south, and they are subjected to such uniform conditions as tend to 
insure stability of type, once adjustment to local environment is accomplished. 
We have here, therefore, either an example of a colony widely separated 
from the parent stock, and remaining inflexible under alien conditions, or 
else an indistinguishable reduplication of another form not closely related in 
time thru the interaction of similar conditions. If the latter supposition be 
the true one, and it probably is, we have in this bird a theoretical sub- 
species, but one which we cannot describe or distinguish in other than geo- 
graphical terms. 
The case is somewhat similar with our Nighthawks (C. virginianius 
subsp.) and Sparrow Hawks (Falco sparverius subsp.), but the problem in 
these instances is further complicated by the opportunities of migration. 
a. “The present example of an isolated colony of a particular form, or what must be regarded as the 
same form in the absence of obvious distinctive characters, is one of several instances which are very 
troublesome to both the systematist and the student of geographic distribution. The birds of this species 
occurring, exclusively, in the area defined above are clearly intermediates between P. a. septentr1onalis, 
a form larger and paler than P. a. atricapillus, which occupies the region immediately eastward, and 
P. a. occidentalis, a form smaller and darker than P. a. atricapillus, which inhabits the region immediately 
westward. It thus happens that, while these puzzling birds are practically, if mot absolutely, indistin- 
guishable from P. a. atricapillus they can hardly be considered exactly the same, since they are everywhere 
widely cut off from the latter by the very extensive area occupied by P. a. septentrionalis."’—Ridgway. 
