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Walworth Counties, east into Brown County, and south through Faulk, eastern 
Potter, and western Spink Counties into eastern Sully, northern Hyde, and most 
of Hand and Beadle Counties, (2) an expansion of the usually medium to high 
density areas of Roberts, Marshall, and Day Counties and Kingsbury, Brookings, 
Miner and Lake Counties through Clark and western Codington and Hamlin Counties, 
(3) an expansion of the usually medium to high density area in Stanley County into 
northeastern Jones County, and (4) the preseace of local medium to high density 
areas in Lyman, Dewey, and Corson Counties. 
Physiographically, the distribution of the breeding duck population was such 
that the highest and very similar duck densities occurred in the James River Valley, 
Missouri Hills, and Prairie Hills (Table I}. Average minimum duck densities were 
23.68 per square mile in the James River Valley; 22.06 in the Missouri Hills; 
21.48 in the Prairie Hills; 10.92 in the Minnesota Valley; and 5.17 on the Missouri 
Plateau. 
All of the physiographic divisions showed substantial increases in duck 
densities over those of 1951. However, the areas showing the greatest relative 
increases where the James River Valley (160 percent) and Missouri Plateau 
(110 percent); while the areas showing the least increase were the Missouri Hills 
(81 percent), Prairie Hills (53 percent), and Minnesota Valley (77 percent). 
Estimates of the minimum duck populations in each of the physiographic 
divisions appear in Table I. These figures reveal that the distribution of the 
breeding duck population in 1952 reflected the usual trend during wetter years of 
increased relative use of the lowlands with a corresponding decrease in the use of 
the hill areas. As a result the James River Valley contained 44 percent of the 
State-wide population in 1952, compared with 35 percent in 1951. The Missouri 
Plateau contained 20 percent of the birds during both years. Decreases in relative 
utilization occurred in the other divisions. The Prairie Hills showed the greatest 
decrease from 24 percent of the State-wide population in 1951 to 17 percent in 1952. 
The Missouri Hills and Minnesota Valley decreased in relative utilization from 
19 percent to 17 percent and from 2 percent to 1 percent respectively. 
species Composition and Densities 
Estimates of the species composition of the breeding duck population were 
based on the number of males of each species observed on the ground transects 
Table (2). Changes in the species composition from that of 1951 were increases 
in the percent composition of the blue-winged teal, pintail, ruddy, and canvasback ; 
and decreases in the relative abundance of the mallard, shoveler, gadwall, redhead, 
and scaup. The species which increased the most in relative abundance were the 
pintail which rose from 19 percent to 25 percent of the population, and the blue- 
winged teal which increased from 41 percent to 44 percent. Substantial decreases 
in percent composition occurred in the mallard, 17 to 15 percent; shoveler 10 to 
7 percent and gadwall, 4 to 3 percent. 
Species densities were used to interpret the significance of changes in species 
composition. These values were calculated by applying each percent of composition 
to the average, minimum, State-wide duck density to obtain a corresponding 
estimate of the density of each species (Table 2). All of the more abundant species 
showed increases in density except the scaup which decreased 62 percent below the 
