BIRD STUDIES IN CALIFORNIA 255 



The eastern desert area, in the southeastern part of the 

 state, is composed maiidy of the Colorado and Mohave des- 

 erts and extends from two-thirds to three-fourths the way 

 across the state, heing bounded on the west by detached des- 

 ert mountain ranges. This is an area of excessive aridity 

 with, in places, an annual rainfall of not more than two 

 inches. Northward, the desert area, now the western mar- 

 gin of the Great Basin, becomes a narrow strip at the foot of 

 the Sierras, but at its northern extreme, broadens to nearly 

 half the width of the state. 



The Sierras form a wall from 70 to 100 miles wide and 

 about 500 miles long on the eastern side of the state, extend- 

 ing from Lassen Peak in the north to Tejon Pass on the 

 south. From the sun-scorched deserts at the east, or more 

 fertile valleys at the west, they rise through a succession of 

 forest growths to alpine meadows and snow-covered sum- 

 mits, with correspondingly wide diversity in bird-life. 



The Sierras mark the eastern boundary of California's 

 great interior valley, which is enclosed on the west by the 

 Coast Range. This — the Sacramento Valle3 r at the north 

 and San Joaquin Valley at the south — is a, generally speak- 

 ing, level area some 500 miles long, and averaging 40 miles 

 wide. It is devoted to grain and grazing. The interior val- 

 ley is bounded on the west by the Coast Eange, which ex- 

 tends from the Santa Barbara region northward the whole 

 length of the state, with a conspicuous break at San Fran- 

 cisco Bay. Heavily forested in its northern portion, it is 

 comparatively arid south of Pacific Grove and, in the dry 

 summer season, its golden brown hill-slopes are one of the 

 characteristic features of the state 's scenery. By no means 

 so high as the Sierras, the Coast Range mountains do not 

 reach above the timberline and no alpine birds are found in 

 them. 



To the west of the Coast Range, lies the coastal strip of 

 valleys and hills, parallel to the mountains. In northern Cal- 

 ifornia, where the land temperature is lower than the sea 



