1926] Swarth: Birds amd Mammals from the Atlin R&gion 81 



of all the forms of Dendragaxpus there is more or less variation with 

 age in the shape of the tail feathers, in the length of the tail, and in 

 the shape of the tail as a whole. 



In the plumage as a whole there is marked seasonal variation, too, 

 that must be taken into account. Birds in fresh fall plumage (both 

 sexes and both the yearlings and fully mature) are of a clearer blue- 

 gray, compared with late spring and summer specimens, in which this 

 color has changed to a dingy brown. 



Fig. E. Tails of Dendragapus fuliginosus sifkensis, showing variation due to 

 sex and age, about % natural size, a, adult male, in second year or older (M.V. 

 Z. no. 133) ; 6, immature male, during first year (M.V. Z. no. 136) ; c, adult female 

 (M.V.Z. no. 134); d, immature female (M.V.Z. no. 135). 



Relative roundness of tail, besides being a marked age character in 

 certain forms, is also a feature in geographical variation. The sub- 

 species howardi was described as having the tail longer and more 

 graduated than sierrae (Dickey and van Rossem, 1923, p. 168), and 

 the comment is made that "throughout the range of D&ndragap'ws 

 obscurus in California there is a gradual geographic variation which 

 particularly affects the length and graduation of the tail. ' ' This same 

 variation can be traced beyond California. From the northern limit 



