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Brood Production Survey 
This is the second year of extensive brood survey in South Dakota. At 
present this survey is limited to the portion of the State east of the Missouri River, 
The survey consists of two phases which, when considered together, provide an index 
to duck brood production. One phase is an extensive aerial survey, which provides 
an index to brood density in mid-July. The second phase is a system of ground 
transects which is run weekly throughout the brood season to obtain an estimate of 
the hatching curve. Calculation of the brood production index is made at the close of 
the brood season. This index consists of the July brood density index increased by 
the percent of the broods that the hatching curve indicates was flying at the time of 
the July survey and the percent that was hatched after the July survey. 
Since the hatching curve cannot be constructed until the end of the brood 
season, only the extensive survey of mid-July brood density is of any value in pre- 
dicting production. Therefore, this report deals only with the mid-July brood density 
survey which serves to compare current brood production through mid-July with 
production during the same period in 1953. 
Methods of Survey 
The July brood density survey is based on the same system of gridded, aerial 
transectsthatis used for the aerial phase of the breeding population survey in May. 
The east-river portions of every other transect are flown. Coverage is made by two 
- pilot-observer teams. The survey was made during the week of July 11-17 in 1954 and 
the week of July 13 - 19 in 1953. Data obtained concerning the density of duck broods 
and water areas appear in Table IV. 
Brood Densities and Trends 
The mid-July, east-river brood survey indicated a minimum brood density 
of 0.65 broods per square mile. This is 8 percent below the 1953 mid-July density of 
0.71 broods per square mile. 
The extreme eastern part of the State, the Minnesota Valley and Prairie Hills, 
had a considerably higher brood density than in 1953. In the Minnesota Valley 0.33 
broods were observed per square mile where none were observed in 1953. In the 
Prairie Hills the observed brood density was 39 percent greater than in 1953. 
The western portion of the east-river country contained considerably fewer 
broods than in 1953. The Missouri Hills showed the greatest decrease with a brood 
density 60 percent lower than that in 1953, The brood density in the James River 
Valley was 36 percent below the density in 1953. 
