Vesper sparrows and western meadowlarks were both 

 found in similar densities on grazed and ungrazed plots 

 (table 2). Both species mainly frequent grasslands and 

 open, low-growing shrub habitats (Ryser 1985). Both for- 

 age and nest on the ground. At Summit Creek, we found 

 vesper sparrows most often in the sagebrush/upland com- 

 munity type. Western meadowlarks were distributed 

 thoughout the grazed and ungrazed plots. Vesper spar- 

 rows and western meadowlarks were negatively affected 

 by livestock grazing in northern Nevada (Page and others 

 1978). In North Dakota, western meadowlarks were about 

 equally common under three levels of grazing intensity 

 (Kantrud 1981), and in Oklahoma, Smith (1940) found that 

 only severe overgrazing made conditions unsuitable for the 

 western meadowlark. 



Red-winged blackbirds were found as breeding birds only 

 on the ungrazed plot (table 2). Conversely, Brewer's black- 

 birds were territorial only on the grazed plot. Nests of the 

 red-winged blackbird were bound to tall, coarse stalks of 

 beaked sedge found in thick stands near the stream. 



Heights of beaked sedge communities in the grazed plot 

 were considerably reduced as a result of livestock grazing, 

 thereby essentially eliminating potential nesting habitat 

 for red-winged blackbirds. Nests of Brewer's blackbirds 

 were on the ground in tussocks of grasses and forbs or 

 beside a clod of dry manure. Taylor (1986) found red- 

 winged blackbirds more abundant in undisturbed or 

 rarely grazed riparian habitats in southeastern Oregon. 

 In North Dakota, Kantrud (1981) found that red-winged 

 blackbird populations were greatly reduced or extirpated 

 by heavy grazing. 



Small Mammals 



Six species of small mammals were trapped during two 

 seasons of study at Summit Creek (table 3). Deer mice 

 and montane voles accounted for over 94 percent of 115 

 individual animals trapped. Each of those species was 

 trapped on both grazed and ungrazed study plots. Other 

 species were caught irregularly and in smaller numbers. 



Table 3 — Relative abundance, naive density, and other attributes of small mammal popula- 

 tions on grazed and ungrazed study plots. Summit Creek, ID, 1988 and 1989 



Relative abundance Naive density^ 



Foraging (n/100 trap nights) (n/ha) 



Species guild^ Ungrazed Grazed Ungrazed Grazed 



Vagrant shrew INS 



1988 



0.2 



0.0 



0.6 



0.0 



1989 



.0 



.0 



.0 



.0 



Water shrew 



INS 









1988 



.2 



.0 



.6 



.0 



1989 



.3 



.0 



1.2 



.0 



Northern pocket gopher 



HER 









1988 



.2 



.0 



.6 



.0 



1989 



.0 



.0 



.0 



.0 



Great Basin pocket mouse 



GRA 









1988 



.2 



.0 



.6 



.0 



1989 



.0 



.0 



.0 



.0 



Deer mouse 



OMN 









1988 



2.7 



5.2 



9.5 



18.3 



1989 



1.3 



4.8 



4.7 



17.2 



Montane vole 



HER 









1988 



1.5 



.8 



5.3 



3.0 



1989 



1.8 



.0 



6.5 



.0 





Total naive density (n/ha) 











1988 





17.2 



21.3 





1989 





12.4 



17.2 





Biomass (g/ha) 











1988 





304 



354 





1989 





283 



282 





Species richness (n) 











1988 





6 



2 





1989 





3 



1 





Species diversity^ {'\rLpf) 











1988 





2.47 



1.31 





1989 





2.33 



1.00 



'After Martin and others (1951), INS = insectivore, HER = herbivore, GRA = granivore, OMN = omnivore. 

 ^After Wilson and Anderson (1985). Effective trapping area and grid size are assumed to be equal. 

 'After Hill (1973). Here, p.is the proportional abundance of the n species in a sample. 



4 



