CALIFORNIA THRASHER 403 



State, with its faunal extension, the northwestern portion of Baja 

 California. The range of the species extends from the western slopes 

 of the Sierra Nevada and the higher mountains of southern Cali- 

 fornia to the Pacific, and from the head of the Sacramento Valley to 

 about latitude 30° in Baja California. 



As pointed out by Dr. Joseph Grinnell (1917), it is predominantly 

 a species of the Upper Sonoran Zone, being most abundant along 

 the bases of the mountains, where it ascends the brushy southerly and 

 westerly slopes to an altitude of at least 5,000 feet in the southern 

 part of the State, but never enters the Transition Zone coniferous 

 forests. Its lower limits, however, are less strictly defined, especially 

 toward the south, where it follows the brush-bordered watercourses 

 down into the Lower Sonoran. Dr. Grinnell suggests that a certain 

 degree of atmospheric humidity may also be a requisite for this species, 

 as it fails to follow the Upper Sonoran Zone aromid the southern end 

 of the Sierra Nevada into apparently suitable territory on the east- 

 ern slope of the range. 



The California thrasher has occasionally been found nesting on the 

 desert side of the San Gabriel, San Bernardino, and San Jacinto 

 Mountains, in the territory of the crissal and LeConte's thrashers, 

 but in general both high mountains and deserts constitute effective bar- 

 riers to its spread. As to its ecological relationships, Dr. Grinnell 

 (1917) says: 



The California Thrasher is a habitual forager beneath dense and continuous 

 cover. Furtliermore, probably two-thirds of its foraging is done on the ground. 

 In seeking food above ground, as when patronizing cascara bushes, the thrasher 

 rarely mounts to an exposed position, but only goes as high as is essential to 

 securing the coveted fruits. The bird may be characterized as semi-terrestrial, 

 but always dependent upou vegetational cover ; and this cover must be of the 

 chaparral type, open next to the ground, with strongly interlacing branch-work 

 and evergreen leafy canopy close above — not forest under-growth, or close-set, 

 upright stems as in new-growth willow, or matted leafage as in rank-growing 

 annual herbage. 



In these favored haunts throughout its range the thrasher is asso- 

 ciated w^ith two other birds of rather similar coloration, the brown 

 towhee and the wren-tit. Like the towhee, the thrasher holds no preju- 

 dice against civilization but becomes a common and by no means shy 

 dooryard resident of the foothill towns. 



In comparing the species of this genus, William L. Engels (1940) 

 writes: "The California * * * thrasher appears to have few 

 characters in common with the brown thrasher : the bill is very long 

 and markedly decurved, sicklelike ; the bird's upper parts are grayish 

 brown and the underparts somewhat lighter in color, but without the 

 dark streaks so distinctive of the brown thrasher. The migratory 

 brown thrasher, in its daily rounds, progresses predominantly by 

 flight; the nonmigratory California thrasher is a swift and skillful 



