Table 28 compares the percent species composition of breeding waterfowl 

 observations made during this study with that of breeding-pair estimates made 

 during other studies in Montana, Saskatchewan, and North Dakota. Breeding 

 waterfowl populations in the study area compare most favorably with those 

 studies by Lokemoen (1973) in the southwest slope region of North Dakota. 

 Lokemoen's study area is very similar to the Circle West study area in top- 

 ography and vegetation, and is also characterized by small, scattered stock- 

 ponds and reservoirs rather than the natural potholes characteristic of 

 Stoudt's (1971) and Stewart and Kantrud's (1974) study areas, and by relatively 

 low waterfowl densities compared to other parts of North Dakota (Stewart and 

 Kantrud 1973). It can be seen in table 28 that the relative abundance of 

 breeding pintails was apparently much lower in the present study than the 

 others listed. Smith (1953) also listed the mallard, pintail and blue-winged 

 teal as the three most important breeders in his eastern Montana study. Pin- 

 tails are early nesters, adapted to capitalize on early, temporary water areas 

 created in May and early June by runoff or spring rains, and are prone to shift 

 to more favorable breeding grounds in years when drought reduces the avail- 

 ability of such habitats (Krapu 1974, 1977, Stout 1971, Stewart and Kantrud 

 1973), as was the case in the study area in 1977. 



Monthly species composition of all recorded waterfowl observations made 

 within the proposed mining area (20% of the total number) during 1977 is shown 

 in table 29. For most species, percent species composition is similar to that 

 of all recorded observations (table 27); exceptions are the gadwall, which com- 

 prises a considerably larger percentage of the mining area observations, and 

 the pintail, which comprises a somewhat lower percentage. Observed waterfowl 

 use of major stockponds in the mine study area is shown in table 30, and breed- 

 ing-pair census data for four of the larger stock-ponds are shown in table 31. 

 It can be seen that waterfowl in 1977 tended to concentrate on the larger 

 stockponds year-round. This is consistent with the findings of Smith (1953) 

 that size is more important than vegetation in determining overall waterfowl 

 use. Breeding populations were small, and were restricted to the vicinity of 

 larger stockponds and creeks having suitable nesting cover. The mallard and 

 American wigeon appeared to be the predominant breeding species in the mine 

 study area, and were the only species of which broods were observed. Except 

 for the apparent breeding of two diving duck species (lesser scaup ana ruddy 

 duck) which were unconfirmed by broods, dabbling ducks were the only breeding 

 species encountered in the mine study area. Data on broods observed is sum- 

 marized in tables 30 and 32, and indicate that breeding was not successful for 

 all censused pairs reported in table 31. 



Suboptimal breeding-season moisture conditions and resultant small sample 

 sizes precluded estimation of breeding density in the study area. However, 

 densities during more favorable years will probably be found to be comparable 

 to estimates of 1.2-3.0 pairs/km^ (3.1-7.8 pairs/mi^) obtained in similar 

 stockpond-dominated habitats in North and South Dakota (Bue et al. 1952, 

 Brewster et al.l976, Lokemoen 1973). One would not expect this region to sup- 

 port the high densities reported by Rundquist (1973) and Stewart and Kantrud 

 (1974) for the glaciated pothole regions of Montana and North Dakota. Berg 

 (1956Kin a study of fenced and unfenced stockponds in the southeastern cor- 

 ner of the reconnaissance study area, encountered only 5 mallard and 2 pintail 

 broods in 12 stockponds averaging 1 ha (3 surface acres) in size; breeding 

 populations of certain stockponds in the mine study area were apparently 



144 



