Fig. 2. Tail of Penthestes gambeli gambeli (no. 27784, Mus. Vert. Zool.; ♂, full-grown juv.; Sierra Ancha, Gila Co., Arizona; June 26, 1917). × 1.00.
Fig. 3. Tail of Penthestes gambeli abbreviatus (no. 24059, Mus. Vert. Zool.; ♂, full-grown juv.; Yolla Bolly Mt., Tehama Co., California; August 5, 1913). × 1.00.
It is improbable that the fact of subspecific differentiation in Penthestes gambeli has been altogether overlooked previous to the present time. A premonition of the geographic variation now formally pointed out is to be found in the early writings of Baird (1858, p. 394), who remarked that "a specimen, apparently of this species [Parus montanus], from Medicine Bow creek [Wyoming], (5643,) though marked female, is larger than those from California, as shown by the measurements." Also, some of the differences in proportions in the subspecies now recognized are shown in the table of measurements given by Ridgway (1904, p. 409).
For a detailed description of the Mountain Chickadee as a species, the reader is referred to Ridgway (1904, p. 408).
Penthestes gambeli gambeli (Ridgway)
Rocky Mountain Chickadee
Parus montanus Gambel (1843, p. 259); and of authors, part. This name preoccupied (see Ridgway, 1904, p. 409).
Parus gambeli Ridgway in American Ornithologists' Union Committee (1886, p. 335); and of authors, part. Substitute name.