221 
Table II. - Breeding Population Aerial Counts, 
a ie mm i 
Eastern Western 
Sandhills* Sandhills ** 
Total study area (square miles) 5,001 12, 384 
Square miles in sample 154.8 297.2 
Total observed ducks 2,091 1, 846 
Ducks per square mile 13.5 6.2 
Duck index (ducks per square mile x study area) 67,564 76,905 
* Includes Wheeler, Garfield, Holt and Rock Counties and Brown County 
east of State Highway 7. Counts made May 11-12, 1954. Conservation 
Officer Von Dane, Pilot and U.S. Game Agent W. G. McClure and 
Writer, Observers. 
** Includes Grant, Arthur, Garden, Sheridan, and Cherry Counties and 
Brown County west of State Highway 7. Counts made June 8 -12, 1954, 
Conservation Officer Von Dane, Pilot and Biologist G. Schildman and 
Writer, Observers. 
Although no comparable data are available to indicate trends, these aerial 
counts are presented as the only available indices to the size of the sandhill breeding 
population. 
The June counts in the western area were found necessary when data gathered 
on a mid-May random sample of lakes proved useless for the establishment of trends 
or indices. A comparison of ground counts made over the same routes in that area 
indicated a loss of 31 percent in total observed ducks from mid-May to mid-June. 
Using this as a correction for the aerial counts would indicate a mid-May breeding 
population in the western sandhills of about 111,000 ducks. 
A statistical analysis of the aerial count data by Dr. Don Kanel, Department 
of Agricultural Economics, University of Nebraska showed the coefficient of 
variation to be plus or minue 28 percent of the estimated total for the eastern area 
and plus or minus 36 percent of the estimated total for the western area. While these 
are in excess of the 20 percent limits of error desired throughout the flyways, it must 
be noted that no correction factors such as those for unobserved ducks, have been 
applied. Therefore, these indices probably represent the minimum breeding popula- 
tion for the sandhills. 
