t may be stated that _Penthestes
gambeli_ including its subspecies is throughout its range non-migratory,
save as a few individuals in pairs or small companies occasionally
descend in fall or early winter to lower levels closely adjacent to
their mountain habitats. The range of the species roughly extends from
and includes the Rocky Mountains to or nearly to the Pacific Coast, and
from Alberta and British Columbia south nearly to the Mexican
line--somewhat south of it in northern Lower California. Within this
general area the Mountain Chickadee is by no means uniformly
distributed. [Page 506] Especially towards the south is its range very
"spotty," the representations on detached mountain tops being wholly
isolated. Two main areas of relatively continuous distribution are,
however, perceivable--the Rocky Mountain area, and the Sierra Nevada
area.

[Illustration: Fig. 1. Map showing distribution of the races of
the Mountain Chickadee in California.]

Close scrutiny of the series of specimens at hand well representing the
entire Rocky Mountain area reveals no variation in phylogenetic
characters from the northernmost to the southernmost stations. All show
in apparently equal degree the long tail and cinnamon tinge of sides and
back, these features together constituting the grounds for separate
subspecific recognition of a Rocky Mountain form. On the other hand, the
Sierra Nevadan center, with its own recognizable race, [Page 507] of
relatively short tail, proves to have two outlying divergent forms.
These three forms are alike in their lack of any cinnamon tinge, this
being replaced in two of them by a buffy tinge and in one form by leaden
gray. The tail in one of the outlying forms is long, in the other short.
The habitats concerned are, respectively, the desert mountains of the
Inyo region of eastern California, and the coastal mountains of southern
California. This differentiation within the Pacific district,
particularly within the state of California, will be better understood
in its geographic bearing by reference to the accompanying map (fig. 1).

The behavior of the tail of _Penthestes gambeli_--long in the Rocky
Mountain district, short in the Pacific district (see figs. 2, 3)--is
paralleled in the _Penthestes atricapillus_ group of chickadees across
the North American continent in about the latitude of the state of
Washington. In the northern Rocky Mountains occurs the race _P. a.
septentrion