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Waterfowl Densities 

A total of 11,830 ducks were observed on the 1065 square miles of aerial 
transects. In the past these data have been used directly to calculate the observed 
state-wide duck density. This year, because only every other transect was flown 
west of the Missouri River, the observed duck density was based on data which 
were inflated to include twice the number of ducks observed west of the river and 
twice the actual west river square-mile coverage. This correction was necessary 
in order to obtain a valid estimate of the observed state-wide duck density which is 
directly comparable to that of previous years. A iotal of 1102 ducks were actually 
observed on the 390 square miles of transects west of the Missouri River. There- 
fore, the raw data were increased by these amounts, resulting in totals of 12,932 
ducks and 1455 square miles of aerial coverage. Thus the 1954 state-wide observed 
duck density was calculated to be 8.89 ducks per square mile. 
The correction factor for hens on nests was 1.22, based on 7564 males and 
5677 females observed on the ground transects. Correction of the observed density 
of 8.89 ducks per square mile by the correction factor of 1.22 results in a minimum 
state-wide duck density of 10.85 ducks per square mile. This is a minimum density 
because a considerable, but undetermined, portion of the birds on aerial transects 
are not observed. From the density of 10.85 ducks per square mile and the 74, 778 
square miles in the State, excluding the Black Hills, the 1954 minimum breeding 
population in South Dakota is estin.ated to be 811,000 ducks or 405,500 breeding 
pairs. 
Waterfowl Density Trends 
The 1954 minimum duck density of 10.85 ducks per square mile or 811,000 birds 
is 21 percent lower than the 1953 minimum density of 13.65 ducks per square mile 
of 1,021,000 ducks. This decrease has reduced the breeding duck population to a 
level that is comparable to the average breeding population over the last four years. 
The current breeding duck density is a non-significant four percent greater than the 
1950-53, four year average of 10.40 ducks per square mile or 778, 000 birds. 
The number of coots observed on the ground transects provides a rough index to 
the breeding coot population. A total of 1779 coots were observed on 517 square 
miles of transect this year, compared with 3295 on 558 square miles of transect in 
1953. Thus, the index to the current population of breeding coots is 3.4 birds per 
square mile or 42 percent below the 1953 average of 5.9 coots per square mile. 
Waterfowl Distribution - Georgraphic 
The geographic distribution of the 1954 breeding duck population is pictured in 
Figure l. 
