73 
It may be noted that the water area indices for previous years have been 
altered. Experiments conducted by J. Lynch have shown that two-thirds of the 
areas falling within a one-eight-mile strip also fall within the one-sixteenth-mile. 
Thus, water area counts made on the one-sixteenth-mile strip on both sides 
(1952 and 1953) were multiplied by the factor 6.75 for comparison with 1954 data. 
(Ponds counted on 1/8 mile on one side). 
There was ample water throughout the area for nesting and brooding probably 
to much water for optimum nesting success. However, by late July when Stratum B 
was flown for broods, water levels had already dropped and the pond index was 
384,200, considerably below the May figure. By the end of July the figure for 
Stratum A had also dropped below that of May, although still highe: than previous 
July readings. 
Breeding Population 
The cool wet spring was reflected not so much in late arrival of birds, as 
in a late start of nesting. Many birds were still concentrated on the larger sloughs 
and gathering places, Even at the start of the air survey, delayed until May 11, there 
were a few birds, mainly diving ducks, which had not yet settled down on the 
nesting grounds, However, by the time the survey was well underway, these birds 
had dispersed and begun their nesting activities. May populations are shown in 
Table III. The lower part of the table shows the 1953 and 1954 data corrected for 
absent hens on their nests. The upper portion of the table shows data for these same 
years made comparable to 1951 and 1952 when Strata A and B data were not corrected 
for absent females. 
Table II]. - May Waterfowl] Population Indices, Southern Manitoba Aerial Survey. 




i Stratum A Stratum B Strata A and B 
Year (10, 368 Sq. Mi.) (28,600 Sq. Mi.) (38,968 Sq. Mi.) 
1951 472, 800 165, 900* 638, 700* 
1952 343,200 1435, 300* 486, 500* 
1953 209,400 117, 300% 326, 700* 
1954 361, 900 165, 900* 527, 800* 
1953 209,400 151,600 361,000 
1954 361,900 242, 800 504, 700 

Percent Change 1953 1954 
73% 60% o5% 
* Data uncorrected for absent hens in these cases. 
