304 University of California Fuhlirations in Zoologi/ [Vol. 16 



thickly together, forming a dense thicket. On some of the very low 

 land near the river there are small meadows where the willows have 

 not been able to establish themselves or from which they have been 

 cleared by man. 



The majority of the species of the willow association are not found 

 in the adjacent sagebrush association and these two associations are 

 very distinct. The species of the willow association in the sagebrush 

 area are all found also in the eottonwood-willow association of the 

 prairie area. 



Twenty-nine traps set at the edge of the willows along the Walla 

 Walla Kiver three miles east of Wallula took, on June 13, 1914, 7 

 Rcithrodontomys megalotis nigrescens, 8 Peromyscus maniculatus gam- 

 helii, and 6 Mus musculus musculus. On June 15, the third day's trap- 

 ping in this trap-line, one Sorex vagrans dobsoni was taken, and also 

 several mice. It is evident that small mammals are much more numer- 

 ous in these willows than in other habitats of the area. This is true of 

 birds also, for more were seen here than elsewhere. 



WATER-M.\RGIN HABITAT AND ASSOCIATION (SAGEBRUSH AREA) 

 Major : 



Thamnophis elegans. Oxyeehus vociferus vociferus — 



summer. 



Minor: 



Scaphiopus hanimondii hammoudii. 



Seported: 



Rana pipiens brachyeephala. Agelaius phoenieeus neutralis — 



summer. 



The water-margin habitat comprises the shores of streams, irrigat- 

 ing ditches, and lakes. Only a few seepage lakes occur in western 

 Walla Walla County and streams and irrigating ditches are not numer- 

 ous. There is a considerable extent of barren sandy and gravelly shore 

 along the Columbia and Snake rivers. Little study was made of the 

 life of those places. Along the Walla Walla River the water-margin 

 habitat is a very narrow strip between the river and the growth of 

 willows. A few bars of mud and gravel occur, but these are not ex- 

 tensive. 



In the sagebrush area the water-margin association is not very im- 

 portant and is made up of only a few characteristic species. 



