Pronghorn were widely distributed throughout the mine study area 

 during the spring through fall period with areas of heaviest use in the north- 

 central and southwestern portions. The southern and central portions of 

 the proposed mining area apparently receive the most use (Figures 5-7). 



BIRD COMMUNITY PARAMETERS 



Waterfowl Communities 



While 1977 was abnormally dry, and waterfowl habitat quality in the 

 study area was relatively poor, 1978 was a wet year (Table 1), and water- 

 fowl use and production was consequently much higher in 1978. Many stock- 

 ponds which were dry in the spring and early summer of 1977 were full or 

 nearly full throughout 1978, providing nearly optimal breeding conditions 

 in the study area. 



Breeding season species composition of all recorded waterfowl and 

 water bird observations is presented in Table 11. Monthly changes in 

 waterfowl species composition, as well as 1977 - 1978 changes, are port- 

 rayed graphically in Figure 8. It is evident that the mallard is the 

 predominant waterfowl species, although it constituted a relatively smaller 

 proportion of the total waterfowl community in 1978. During both years, 

 the mallard, American wigeon, and blue-winged teal, northern shoveler, 

 gadwall, pintail, and lesser scaup showed an increase in 1978. Species 

 composition in 1978 was similar to that reported by Rundquist (1973) in 

 a Phillips County, Montana study. 



Waterfowl breeding season census data for the proposed mining area 

 and mine study area are summarized in Table 12. These data are converted 

 to production and density estimates in Table 13. It can be seen that the 

 densities of pairs and broods on the mine study area are lower than estim- 

 ates reported for similar habitats by Bue et al . (1952), Gjersing (1971), 

 Lokemoen (1973), and Brewster et al . (1976). The proposed mining area, 

 however, supported breeding waterfowl densities roughly twice those of 

 the mine study area; these densities are near the low end of the range 

 for the other studies mentioned above. In terms of density per unit water 

 area, the proposed mining and mine study area compare favorably to estim- 

 ates reported for other areas. 



Data on broods observed during 1978 are presented in Table 14. 



35 



