
43 
Relationship of Aerial to Ground Coverage of Breeding Population 
Sa a a i ee ee re core ee OPA SLOT 
At least two aerial censuses were flown of each study area to ascertain 
breeding populations during the month of May. Comparative results of the aerial 
and ground surveys conducted during the population peak are recorded in Table IX. 
Aerial observations used in Table 1X above, were made under con- 
ditions nearly identical to those of 1954, The new emergent growth and edge 
vegetation on the prairies had not yet begun to appear. In the parklands the same 
situation existed; and, in addition, the aspen had not begun to leaf. In all cases, 
the aerial observers increased their percentage of total birds counted this year. 
On the two prairie study areas, this was particularly noticeable. Observations on 
Area I were still inferior to those obtained in past years, but water conditions were 
enough like those of 1954 to account for some of the discrepancies between ground 
and aerial counts. Many of the mallards and pintails fly on and off the area toa 
large lake near the study area which makes for a considerable difference in ground- 
air figures because of the total passage of time between a near-instantaneous aerial 
count, as opposed to a ground count of several hours. 
Table X. - Comparison of Ground and Air Brood Counts. 
Percent Seen by Air 
Area Ground Air First Run Second Run 
I No broods or water No broods or water 0 0 
II 51 (7/15) 62 (8/1) 42 (7/19) 52(7/29) 82% 84% 
Ill 82 (7/12) 174 (7/29) 30 (7/12) 121 (7/29) 37% 70% 
IV 88 (7/8) 190 (7/29) 56 (7/9) 82 (7/29) 64% 43% 
Low water levels and the concentration of broods in the remaining 
potholes on Area II contributed markedly to the high aerial count of broods in this 
prairie region. Excellent visibility, plus the early hour and normal movement of 
broods into open water later in the season resulted in a high percentage of broods 
being seen on Area [II late in July. 
Several experimental flights were made during the brood season for 
the purpose of analyzing such factors as weather, time of day, width of transect, 
visibility of species by age class, and visibility in different habitat types. This 
data will be analyzed elsewhere and cannot be included in this report. We have, 
however, reached the stage where we can try to measure these factors and now 
have amassed sufficient data to begin an analysis of it, Consistent use of the same 
aerial observers, attention to time of day, light conditions and wind speeds are 
proving to be of great value in gathering better brood data from year to year. An 
analysis of data already gathered should be of great value to all agencies cooper- 
ating in these studies and should vastly improve future surveys of the same type. 
