
Production Data 

The 1957 mid-July survey indicated an average observed 
density of 0.400 broods per square mile (Table 5). This is 19 percent 
above the 1956 average of 0.336 broods per square mile and 25 percent 
below the 1953-56, four-year average of 0.533 broods per square mile. 
The physiographic distribution of duck broods is shown in 
Table 5. i‘ 
Average mid-July brood densities indicate large increases 
ix brood production for the James River Valley (+ 123%) and Missouri 
Hills (+ 152%}. Large de¢creases in production were indicated for the 
Minnesota Valley (= 100%) and Prairie Hills (- 55%). 
The average 1957 mid-July brood size (all species) for 243 
broods was 7.8i young per brood. This is 22 percent above the average 
1956 brood size of 6.37 young per brood, and 7 percent above the 1953- 
56, four-year average brood size of 7.32 young per brood. _ 
Table 5 - Mid-July Indices to Brood Densities and 1956-57 Trends in 
Eastern South Dakota 


Duck Broods 
Physiographic : | Per Square Mile Percent 
Division 1956 -- 1957 | Change 



Minnesota Valley 0,111 0.000 100 
Prairie Hills 0.788 0.353 = 55 
James River ‘Valley 0.132 0.295 + 123 
Missour: Hills 0.300 0.757 + 152 
East-River Totals 0.336 0.400 + 19 

Conclusions 
The favorable outlook for brood production may be sufficient 
to offset the effects of the reduced breeding population for 1957. On this 
basis, it is estimated: that-the 1957 fall flight will be approximately equal 
to 1956. 
— «60 
