274 THE CHICKADEE. 



General Range. — Eastern Nortli America north of the Potomac and Ohio 

 \'alleys. "A separate 'colony' inhabits the area between the Rocky Mountains 

 and the Cascade Range, in eastern Washington (Walla Walla. EUensburg, etc.), 

 western Idaho ( Lemi, Fort Sherman, etc.), and central British Ci>lumbia ( Sica- 

 mores [Sicamoos]. Clinton, Ashcroft. etc.).*" — Ridgway. 



Range in Washington. — As above. 



Authorities.—/', a. occidcntalis Brewster, B. N. O. C. VII. 1882, 228 

 (Walla Walla). J. If this colony ]M-oves to Ije completely isolated, as claimed, 

 the bird should. ])erha])s, be separately named, and I would suggest Pciithcstcs 

 atricapilliis fortiiitiis. 



Specimens. — B. I''. 



THE Chickadees of eastern Washington, east of the Cascade foothills, 

 along with those of northeastern Oregon, western Idaho, and southwestern 

 British Columbia, are n(.)taljly larger and brighter than P. a. occidcntalis. 

 In these and other regards they exactly rei)roduce the characters of P. 

 atricii/^illiis. which is a Ijird cif the eastern United States, and from which 

 they are widely separated b_\- P. a. scfifcntrionalis. Now Chickadees are 

 resident wherever found. The most severe winters do not suffice to drive 

 them south, and they are subjected to such imiform conditions as tend to 

 insure stability of type, once adjustment to local environment is accomplished. 

 W'c ha\'e here, therefore, either an example of a colony widely separated 

 from the parent stock, and remaining inflexible under alien con<lititins, or 

 else an indistinguishable reduplication of another form not closelv 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 Ijird a theoretical sub- 

 species, but one which we cannot describe or distinguish in other than geo- 

 graphical terms. 



The case is somewhat similar with mn- Nighthawks (C. virgiiiianns 

 suhsp.) and Sparrow Hawks I Falco sf^arvcriiis siibsf^.), but the problem in 

 these instances is further complicated by the o])portunities of migration. 



a. "The present example of an isolated colony of a particnlar 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. scpteutx\onaIis, 

 a form larger and paler than P. a. atrical'iUus, which occupies the region immediately eastward, and 

 P. a. occidcvtalis, a form smaller and darker than P. a. atricaf^ilhis, which inhabits the region immediately 

 westward. It thus happens that, while these puzzling birds are jiractically, if not absolutely, indistin- 

 guishable from P. (I. atricapilhis 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. 



