514 SwARTH, California Forms of Psaltriparus. [oct. 



coast of Mendocino County have faded on the upper parts to the 

 exact color of July adults from the Sierras, though southern Cali- 

 fornia birds of the same date are darker colored. On the lower 

 surface, however, the Mendocino birds are distinctly dark, quite 

 different from the gray calif ornicus. 



On the whole, of course, these coast birds are representative of 

 minimus, but there is not nearly the difference between minimus of 

 the northern coast district and californicus of the Sacramento Valley, 

 to the eastward, that there is between southern California mijiimus 

 and californicus of the southern Sierra Nevada. 



Ridgway (1884, p. 89), in an early paper on the species, comments 

 upon the paler colors of Marin County specimens, as compared 

 with typical minimus, disposing of the question by regarding these 

 birds as intergrades toward the grayer californicus, the range of 

 which he at that time considered as including the coast of Cali- 

 fornia south of San Francisco Bay. As the more southern birds are 

 now known to be of the race minimus, and as, in fact, specimens 

 from the southernmost extremity of the range of the subspecies 

 are as dark colored as any, this explanation no longer holds. The 

 possibility suggests itself that from the extremely narrow delimi- 

 tations of the range of minimus in Marin, Sonoma, and southern 

 Mendocino counties, compared with the vast area of country 

 directly to the eastward swarming with bush-tits of the subspecies 

 californicus (for, unlike the San Joaquin Valley, the Sacramento 

 Valley presents conditions peculiarly favorable to the species), 

 there is a constant influx of individuals of the more numerous race, 

 californicus, continually encroaching upon the limited territory of 

 the coast form. If the latter occupied a wider area the appearance 

 of intermediates along the border line would not be particularly 

 exciting of comment, but from the nature of conditions at this point 

 these paler colored birds are distributed over the entire width of the 

 restricted coast strip. It seems, in fact, as though there was here 

 something similar to certain cases commented upon by Grinnell 

 and Swarth (1913, p. 393), among problems concerning the distribu- 

 tion of various animals in the San Jacinto Mountains, California, 

 where, from the narrowness of the region of blending of closely 

 related subspecies, peculiar conditions ensue. 



Among other observed results, types of either one of two strongly 



