152 
3. Water area data from 309.1 square miles of ground transects which had 
been run in both 1949 and 1950 showed a 68 percent increase in the density of water 
areas, This spring there was an average of 5.2 water areas per square mile as. 
compared with the 1949 density of 3. l-water areas per square mile. 
4. The average minimum duck density on a State-wide basis, as indicated 
by 1,488 square miles of gridded aerial transects, was 7.91 ducks per Square mile. 
This value includes females which were on the nest at the time of the survey and so 
were not observed. The correction for the unobserved females, based on the observed 
sex ratio obtained by the ground transects, was plus 20.0 percent of the ducks observed, 
5. The distribution of the breeding ducks was obtained from the aerial water- 
fowl and water area survey. This survey showed what is believed to be the usual 
relatively medium and high duck densities in the Coteau des Prairie and the Leola Hills, 
Surrounding the Leola Hills and extending south through Faulk County to northern Hyde 
and Hand Counties was a large area of high duck density that is not considered normal 
and which is attributed to the large increase in the amount of water present this spring 
and the late breakup of water areas in the northern Coteau des Prairies and possibly 
areas to the north. Two other areas of high duck density occurred to the south, one 
west of the Missouri in eastern Stanley and northern Lyman and Jones Counties and one 
east of the Missouri in eastern Buffalo and Brule and western Jerauld and Aurora 
Counties. 
6. Population trends on 309.1 square miles of ground transect run in both 
1949 and 1950 were increases of 29 percent in the number of total pairs and 22 percent 
in total ducks. The density of coots on these transects was exactly double the 1949 
density. 
7. Trends in the species composition of the ducks on the ground transects 
which were run in 1949 and 1950 showed changes for three species. The blue-winged 
teal decreased 2 percent and the pintail and ruddy duck both increased 1 percent in 
respect to their percent composition of the total population. 
8. Brood "censuses" on 147.5 square miles of ground transects in 14 
counties indicated an average breeding-pairs-per-brood index of 19 and an average 
brood density index of 0.83 brood per square mile. No data are available for 
comparison with previous years. 
9. Complete counts of the size of 527 duck broods of 9 species indicated 
an average size for all species ang age classes of 7.02 ducklings per brood. For all 
species the average brood sizes for the 3 age classes were Class l, 7.37; Class 11, 
6.84; and Class 111, 6.70 ducklings per brood. No data from previous years are 
available for comparison. 
