97 
Brood Census 
Table I also shows the number of broods produced yearly. The number of broods 
per square mile in 1954 took a very severe drop when the total brood figure is 
compared to 1952 or 1953. Only 30.7 brood per square mile were noted in 1954 as 
compared to 60.2 in 1953 and 49,2 in 195Z, The 1954 figures indicate a reduction of 
49 percent in the number of broods per square mile, as compared to the previous 
year. The major drop in brood numbers has occurred in the upland nesting species. 
No appreciable drop was noted in the diver production as the number of broods 
remained almost the same as last year. However, dabbler brood Numbers were 
reduced more than 60 percent from last year. 
Rising water levels, rain, snow, predators, and the general inclement weather 
undoubtedly caused a great deal of nest destruction, which was in turn reflected in 
end production. Many dabbler nests were flooded during the heavy June rains, while 
divers were not affected by rising water levels. 
Three complete brood census were carried out on the area, one on July 12, the 
second on August 5, and the last on August 16. The "beat out'' method was used, 
wherein two men walked through all the emergent vegetation of the pothole and flushed 
all broods. Flushed and feigning females were also recorded as broods. There are 
certain inherent faults in this method but it is the most efficient of any and has been 
used successfully for three years, Duplicate broods were removed from the final 
figure in the second and third census after a method described by Blankenship et al. 
(1953 - Techniques for brood production studies). —* 
Summary and Outlook 
1. The number of breeding pairs was somewhat higher in 1954 than in 1953. 
Z. The number of broods produced in 1954 was 49 percent less than in 1953. 
Dabbler production suffered most. 
3. The season was about a week to ten days later, phenologically, than last year. 
Acknowledgments 
The author wishes to express his sincere thanks to the Delta Waterfowl Research 
Station for financial and other aid, to the National Research Council of Canada for aid 
in buying boom traps, and to the members of the Manitoba Game and Fisheries Branch 
and U. S. Fish and Wildlife Service for help in the field. 
