General remarks.--In making use of the intrinsic color characters, which are important here in distinguishing subspecies, it is, of course, essential that the effects of extraneous factors be taken into account. Prolonged wear and fading evidently serve to weaken the intensity of the color tones, more especially the buffy ones. Then, too, chickadees seem peculiarly susceptible to discoloration by smoke, soot and charred wood; for example, our series from Cisco and Blue Cañon, stations along the Central Pacific Railway over the Sierra Nevada, even though taken in September and October almost immediately after completion of the fall molt, are obviously more or less begrimed with soot. On the other hand, the autumn- and winter-taken series from the Yosemite region and from the Siskiyou Mountains are clean, and show their intrinsic color tones to good advantage.
Intergradation undoubtedly connects the four races of the Mountain Chickadee into a continuous series of forms. Abundant material at hand from that portion of the Sierra Nevada immediately south of Mount Whitney shows complete transition from Penthestes gambeli baileyae to P. g. abbreviatus; in fact, many of the specimens can only be placed arbitrarily in one category or the other. Several examples from the vicinity of Mono Lake, in Mono County, California, and from along the west flank of the Sierras in Inyo County, insensibly bridge the interval between P. g. abbreviatus and P. g. inyoensis, especially when considered in connection with the individual variation to which each race is subject in about normal degree.
Material at hand from different parts of the Great Basin is unsatisfactory either in that it is scanty or because of the worn state of the plumage. A summer-taken series of 13 Mountain Chickadees (nos. 8952-8964, Mus. Vert. Zool.) from the Pine Forest Mountains, Humboldt County, Nevada, shows in color no approach to P. gambeli gambeli. In this respect it is like P. g. inyoensis, but the tail averages nearly as short as in P. g. abbreviatus. Taking all features into account it seems best placed under abbreviatus. Fresh-plumaged fall specimens from this locality would make determination more certain.
A specimen (♂, no. 547, Mus. Vert. Zool.) from Anthony, Baker County, Oregon, taken October 16, 1907, might be referred to P. g. abbreviatus; but the tone of color of back and sides is much darker than usual in that form. It is certainly much darker than in P. g. inyoensis. Its tail is but 65.3 mm. long. A skin (♀, no. 18, Morcom coll.) from Camp Harney, Harney County, Oregon, February 17, 1875, has a tail length of 67.7 mm., and in depth of color is about intermediate between abbreviatus and P. g. gambeli. A specimen (♀, no. 136639, U. S. Nat. Mus., Biol. Surv. coll.) from Fort Spokane, Lincoln County, Washington, September 28, 1890, is almost identical with gambeli in coloration; but it, too, has a short tail, only 64.4 mm. long, though there is chance of error here, as several of the rectrices are missing. The writer prefers to leave these last three examples for the time being unplaced.
It is clear that intergradation between Penthestes gambeli gambeli and any one of the other three subspecies is less well established than between any two of these other three. But sufficiency of material from the proper localities through eastern Oregon and eastern Washington would likely prove its existence as is the case between the California forms.
Measurements (in Millimeters) of Selected Specimens Representing the Four Races of Penthestes gambeli
| [U. S. N. M. no.] | Penthestes gambeli gambeli | ||||||
| Sex | Date | Locality | Wing | Tail | Exposed culmen | Depth of bill | |
| 160697 | ♂ | Nov. 24, 1892 | Boulder, Colo. | 71.7 | 71.2 | 8.8 | 4.0 |
| 109948 | ♂ | Oct. 8, 1886 | Pueblo, Colo. | 72.0 | 72.4 | 8.4 | 3.9 |
| 109949 | ♂ | Oct. 5, 1886 | Pueblo, Colo. | 70.9 | 70.3 | 8.5 | 4.0 |
| 176650 | ♂ | Sept. 23, 1888 | Madison E., Gallatin Co., Mont. | 68.0 | 67.8 | 8.9 | 4.1 |
| 124151 | ♂ | Sept. 15, 1888 | Jefferson E., Gallatin Co., Mont. | 69.7 | 67.7 | 10.0 | 3.6 |
| 188823 | ♂ | Oct. 15, 1902 | Mammoth Hot Springs, Wyo. | 68.1 | 67.0 | 9.0 | 3.6 |
| 62546 | ♂ | Nov. 17, 1872 | Filmore, Utah | 69.8 | 68.3 | 8.3 | 3.5 |
| 136638[1] | ♂ | Sept. 27, 1890 | Sawtooth Lake, Idaho | 68.1 | 69.7 | 8.8 | 3.8 |
| 228227[1] | ♂ | Sept. 14, 1910 | Teton Pass, Wyo. | 71.2 | 70.4 | 8.3 | 3.6 |
| 193086[1] | ♂ | Nov. 6, 1903 | Manzano Mts., N. Mex. | 71.4 | 70.6 | 7.8 | 4.0 |
| 184653[1] | ♂ | Oct. 22, 1902 | Corona, N. Mex. | 69.0 | 71.0 | 9.0 | 4.1 |
| 192942[1] | ♂ | Oct. 10, 1903 | Twining, N. Mex. | 72.0 | 71.4 | 8.5 | 4.0 |
| 136637[1] | ♂ | Sept. 18, 1889 | San Francisco Mt., Ariz. | 71.3 | 70.3 | 7.8 | 3.8 |
| 205661[1] | ♂ | Sept. 10, 1909 | Kaibab Plateau, Ariz. | 73.5 | 74.3 | 8.3 | 4.0 |
[1] Biol. Surv. Coll.
| Mus. Vert. Zool. no. | Penthestes gambeli inyoensis | ||||||
| Sex | Date | Locality | Wing | Tail | Exposed culmen | Depth of bill | |
| 28751 | ♂ | July 24, 1917 | White Mts., Mono Co., Calif. | 73.0 | 72.4 | 7.9 | 3.7 |
| 28760 | ♂ | July 29, 1917 | White Mts., Mono Co., Calif. | 71.0 | 67.0 | 8.0 | 3.6 |
| 28766 | ♂ | July 31, 1917 | White Mts., Mono Co., Calif. | 72.4 | 67.5 | 8.8 | 3.5 |
| 28767 | ♂ | Aug. 18, 1917 | White Mts., Inyo Co., Calif. | 69.4 | 68.1 | 8.0 | 3.7 |
| 28770 | ♂ | Sept. 29, 1917 | Panamint Mts., Inyo Co., Calif. | 68.8 | 69.8 | 8.1 | 3.7 |
| 28771 | ♂ | Oct. 2, 1917 | Panamint Mts., Inyo Co., Calif. | 71.4 | 70.2 | 7.4 | 4.0 |
| 28773 | ♂ | Oct. 2, 1917 | Panamint Mts., Inyo Co., Calif. | 72.7 | 71.0 | 8.4 | 3.8 |
| 28774 | ♂ | Oct. 2, 1917 | Panamint Mts., Inyo Co., Calif. | 69.0 | 66.0 | 8.1 | 3.7 |
| 28781 | ♂ | Oct. 5, 1917 | Panamint Mts., Inyo Co., Calif. | 71.0 | 70.0 | 8.3 | 3.7 |
| 28782 | ♂[2] | Oct. 7, 1917 | Panamint Mts., Inyo Co., Calif. | 72.0 | 71.5 | 8.4 | 3.5 |