numbers of most diving ducks, which require emergent vegetation as nesting 

 cover. Of stockponds in the mine study area, MA07, MC05, MC06, MC07, NCOl , M 

 NC02, NC04, NC06, and NC09 appear to have characteristics most favorable to ^ 

 waterfowl (table 3). 



Breeding Bird Census 



Table 33 summarizes results for the five breeding bird census plots, as 

 well as species diversity (H'), total density, total biomass, single-species 

 dominance, and two-species dominance for each plot and for the five plots com- 

 bined (a more complete account is given in Appendix F). An adjusted number of 

 species is also presented for comparison with other studies. Table 6 summarizes 

 the percentage of representation by the various habitat categories within each 

 plot. 



Two grassland bird species, the western meadowlark and horned lark, were the 

 dominant species of the five combined plots; both were present in fair numbers 

 on the grassland and coulee plots, but only one pair of horned larks was en- 

 countered on the sagebrush plot. Western meadowlark densities were considerably 

 greater than tnose reported by Feist (1968). Four shrub-nesting species, the 

 mourning dove, eastern kingbird, brown thrasher, and loggerhead shrike, were 

 closely associated with dense slumps of tall shrubbery, especially silver buf- 

 faloberry, and were absent from the two grassland plots where shrubs were lack- 

 ing. The yellow warbler, yellow-breasted chat, and rufous-sided towhee were 

 found only on the silver buffaloberry-red osier dogwood coulee grid. Their 

 occurrence and that of red osier dogwood and other dense coulee shrubbery both g 

 appear to be related to the relatively cool, shady, and moist conditions af- " 

 forded by the steep-walled coulee dissecting this plot. Say's phoebe and rock 

 wren territories were also found only on this plot, which provided suitable 

 nest sites in the high, steeply eroded sandstone walls of the coulee. Brewer's 

 sparrow and common yellowthroat territories were found only on the sagebrush 

 plot. The nesting habitat preferences of the Brewer's sparrow, which are met 

 by dense stands of silver sagebrush in this area, are well known (Best 1972). 

 The indicated density of this species in the third of the sagebrush plot which 

 actually is dominated by sagebrush was 114 territories/km^ (45/100 acres, which 

 compares favorably to densities of 74-124/km (30-50/100 acres) reported by Best 

 (1972), Feist (1968), and Schroeder and Sturges (1975) in several other unsprayed 

 sagebrush flats in eastern Montana. The common yellowthroat was restricted to 

 dense clumps of snowberry and rose along the stream channel bisecting the sage- 

 brush plot. Chestnut-collared longspur density was greatest on the needle-and- 

 thread-blue grama grassland plot, which apparently provided the most suitable 

 habitat for the species. Lark bunting colonies were closely associated with 

 fairly open stands of silver sagebrush, and were largest on the sagebrush plot. 

 Vesper sparrow densities were surprisingly low, especially on the sagebrush 

 plot; similar sagebrush habitats in central Montana were found by Best (1972) 

 and Feist (1968) to harbor much greater densities of this species than the 

 plot studied here. Species composition of the needle-and-thread--blue grama 

 grassland plot was similar to that reported by Randall (197b) for a plot in 

 Richland County, Montana. 



Using the plot numbers indicated in table 33, the five plots may be generally, 

 ranked in order of decreasing number of species, total number of territories, f 



150 



