Notes on the Plumage of North American Birds 17 



(3) Yukon Chickadee (P. a. turneri). A large form, paler even than the Long- 

 tailed Chickadee, which inhabits northern and western Alaska. 



Carolina Chickadee (Penthestes carolinensis carolinensis. Fig. 5). 

 Although this species so closely resembles the Black-capped Chickadee that it 

 might well be considered niereh' a race of it, the two kinds do not intergrade. 

 During the winter they may both be found in a narrow strip of territory at the 

 northern limit of the range of the southern species and the southern limit of 

 the range of the northern species. Under these circumstances, it requires a 

 highly trained eye to distinguish these birds by the slight difference in their 

 size and markings, the Carolina Chickadee being smaller and without whitish 

 margins to the wing-coverts; but to one familiar \Aath their notes field identi- 

 fication is possible. 



Two races of the Carolina Chickadee are known: (i) the Florida Chickadee 

 {Penthestes carolinensis impiger), a small, dark form from east-central Florida, 

 and (2) the Plumbeous Chickadee {P. c. agilis), a larger, paler form from the 

 western part of the lower Mississippi Valley. 



Mexican Chickadee {Penthestes sclateri. Fig 3) . This, the most southern- 

 of the Chickadees, may be known by its dark gray, sides and large black throat 

 patch. No races of it have been described. 



Mountain Chickadee {Penthestes gambeli gambeli. Fig. 6). The white 

 line over the eye at once distinguishes this Chickadee, of which one race is 

 known, Bailey's Mountain Chickadee {Penthestes gambeli baileyce), of the 

 "mountains of the great Basin region and northern Lower California, 



Alaska Chickadee {Penthestes cinctus alascensis. Fig. i). This is an 

 Alaskan form of a Siberian species, which resembles the Hudsonian Chickadee, 

 but is paler and has the sides of white instead of gray. 



Acadian Chickadee {Penthestes hudsonicus littoralis. Fig. 2). This species 

 may be known by its brown crown, brownish back, and rusty sides, which are 

 evident in the field. In the interior of Canada and northwest to Alaska, it is 

 replaced by the closely allied Hudsonian Chickadee {Penthestes hudsonicus 

 hudsonicus) , a larger, somewhat more brightly colored race. 



Chestnut-backed Chickadee {Penthestes rufescens. Fig. 7). This distin- 

 guishing character of this species is expressed in its common name. As stated 

 by Professor Cooke on the preceding page, four forms of it are known of 

 which the California Chickadee {Penthestes rufescens neglectus), has only a 

 tinge of rusty on the flanks, and Barlow's Chickadee {P. r. harlowi), has no 

 rustv on the flanks. 



