148 
ground transects in 14 counties in the northeastern quarter of the State were rerun 
August 9-12 during what was believed to be the peak of the hatch. The runs were made 
from daylight until 8:00 a.m. and from 6:30 p.m. until dark. The coverage obtained 
was 147.5 square miles. The information recorded was the number of broods that 
could be seen from the road by inspecting all water areas with binoculars, 
Counts of the sizes of duck broods were made whenever broods were observed. 
The data were recorded by species and age classes, These counts were made mostly 
during the early morning and evening hours from June 11 to August 31. Broods were 
classified as complete or incomplete counts depending on whether or not it seemed 
probable that all of the ducklings in the brood were visible at the time of the count, 
Weather and Water Conditions 
Low temperatures and frequent storms made the spring of 1950 a poor one 
for waterfowl nesting. The average temperatures for March, April, May, and June 
were 7.0, 7.8, 3.9, and 0.2 degrees below normal respectively. April was one of the 
coldest months on record. Precipitation was 0.75 inch above normal in March, 0.79 
inch below in April, 0.33 inch above in May, and 2.14 inches below in June. A 
blizzard on March 6-7 may have been the most severe on record for eastern South 
Dakota. Snow storms occurred on March 25-27, April 10, 24-25, and 29, and May 5, 
7-8. Strong winds and hail hit the northern Coteau des Prairie on June 22-24, This 
adverse weather during the spring resulted in later spring migration and what appeared 
to be a three-week set-back in breeding activity, especially in the northern Coteau des 
Prairie. 
Trends in the density of water areas were calculated from the ground transects 
which had been run in 1949. In 1949 there was an average of 3.1 water areas per square 
mile. This year the average density was up 68 percent, or 5.2 water areas per square 
mile. This trend was general over the northeastern quarter of the State. Only 3 of the 
22 transects showed a decrease in water area density. The increase in water area 
density, accompanied by an increase in ducks, resulted in practically the same degree 
of occupancy as existed in 1949. In 1949, 80 percent of the water areas were occupied; 
this year the percent of occupancy was 79. 
Population Levels, Distribution, and Trends 
The aerial waterfowl and water area survey covered 1, 488 square miles of 
gridded transects. On this area 9, 804 ducks were observed, indicating an average 
density of 6.59 ducks observed per square mile. This value does not take into con- 
sideration females on the nest. The ground transect data indicate that at the time of 
these surveys 20.0 percent of all the birds observed were lone drakes, each repre- 
senting an absent female. To correct for females on the nest, the average density 
of observed birds was multiplied by 1.20. The product indicates an average State- 
wide density of 7.91 ducks per square mile. It should be kept in mind that this value 
represents the minimum average density of ducks because in aerial transect work a 
certain undetermined but substantial portion of the ducks are not seen, 
Figure 2 indicates the distribution of breeding ducks in South Dakota, as 
indicated by the aerial transects. The figures plotted are the number of ducks actually 
observed per 12-mile segment of transect (6 square miles) with no correction for 
fernales on the nest. 
Trends in the population levels of waterfowl were determined from the ground 
transects because there were no comparable data for the aerial transects in 1949. 
Changes in the density of breeding waterfowl were calculated from the ground transects 
which were run in both 1949 and 1950. The counties represented are indicated in 
