The Subspecies of the Mountain Chickadee

Excerpt

Fieldwork was carried on by the California Museum of Vertebrate Zoology during 1917 in the Inyo region of eastern California. In going over the collection of birds obtained, the attention of the writer was arrested by certain peculiarities evident in the Mountain Chickadees. Comparison with series from the Sierras showed the Inyo birds to be paler colored and longer tailed; and in order to appraise these differences in taxonomic terms it became necessary to assemble material representative of the entire range of the species, in so far as possible. The results of the study thus undertaken are presented herewith.

The material involved in the inquiry has amounted to 464 skins of the Mountain Chickadee, derived from the following sources other than the Museum of Vertebrate Zoology: United States National Museum, through Dr. Charles W. Richmond; United States Biological Survey, through Mr. Edward W. Nelson; and the private collections of Messrs. Edward R. Warren, Joseph and John W. Mailliard, G. Frean Morcom, Harry S. Swarth, and J. Grinnell.

As of general interest, and in the nature of an introduction to the systematic analysis to follow, it 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. 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.

Fig. 1. Map showing distribution of the races of the
Mountain Chickadee in California.
Click on map to view larger version.

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, 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. septentrionalis, with long tail; in the Pacific Coast strip of Washington and Oregon occurs the race P....