1908] Grinnell_—Biota of the San Bernardino Mountains. Vl 
is chiefly upper Sonoran below an altitude of 7500 feet, save for 
the immediate bed of the valley, which is Transition in most 
places. (See pls. 1, 2, 6, 10, 22, 23.) 
This Upper Sonoran intrusion along the north wall is char- 
acterized by the usual chaparral association of plants, as listed 
elsewhere for the Pacific slope, except that toward its east end 
the more arid conditions seem to account for an extensive ad- 
mixture of pinon and service-berry. Such Upper Sonoran birds 
as the Bell sparrow, black-chinned sparrow, spurred towhee, San 
Diego wren, pallid wrentit, California jay, California bushtit, and 
dusky poorwill, were regularly noted there during the breeding 
season; while among mammals and reptiles the Merriam chip- 
munk, True white-footed mouse, brown-shouldered lizard, and 
Blainville horned toad appeared to be characteristic. 
Along the bed of the valley and up the north-facing south wall 
extends an almost continuous though not dense Transition-zone 
forest. This consists largely of the yellow and Jeffrey pines, with 
a lesser amount of sugar pine, and, along streams, incense cedar ; 
while on the most shaded slopes the silver fir prevails. On the 
benches or flats black oaks are the only deciduous trees present, 
they being interspersed with conifers. Along the streams cotton- 
woods of two or three species, alders and willows are abundant. 
In the dryer open woods, birds are plentiful, especially chicka- 
dees, nuthatches and woodpeckers. Along shaded streams the 
rarer Sierra hermit thrush, calliope hummingbird, Townsend soli- 
taire, and dipper build their nests; while throughout this wooded 
tract generally the gray flycatcher, western bluebird, Audubon 
warbler, Cassin purple finch, and many other Transition-zone 
species are characteristic and abundant. Along streams the Mo- 
jave wood rat and Rowley white-footed mouse are numerous, and 
in the higher woods the gray squirrel and San Bernardino chip- 
munk, the latter almost always above 7500 feet altitude. 
The above brief outline gives but a very limited idea of the 
biotic complexion of the upper Santa Ana valley. The fact that 
a three hours’ walk from the stream may lead one through three 
distinct life-zones, each with an almost totally distinct flora and 
fauna, will give the reader an idea of the great variety of life 
within a short distance. 
