

87 
The number of breeding pairs per square mile for the past four 
years is shown in Table I. There were no major fluctuations in the total number 
of breeding pairs per square mile during 1952, 1953 and 1954, but in 1955 the 
number of breeding pairs was 25 percent less than in 1954. The reduction was 
noted in all species except gadwall and ruddy duck. 
Boom-trapping operations which were started in May did not appear 
to have any influence on population levels. The general decrease of waterfowl was 
noted in surrounding areas where such trapping was not carried on. 
Brood Gensus 
Three brood censuses were made of the study block, one on July 4, 
the second on July 25, and the third on August 30. All water areas were censused 
by the beat~-out method (i.e. two or three men walked through all the emergent 
vegetationin the pothole). Flushed and feigning females were recorded as broods. 
During the second and third census all broods that appeared to be duplicates of the 
previous census were not added to the final tally. This method followed closely 
that outlined by Blankenship et al "Techniques for Brood Production Studies" and 
by Gollop and Marshall, "A Guide for Aging Duck Broods in the Field." However, 
even the beat-out method, does not yield complete counts. Therefore, all broods 
that were known to be on potholes the day prior to the beat-out, but which were not 
seen during the beat-out itself, were included in the final brood production figure. 
The final number of broods per square mile produced in 1955 is also 
shown in Table I. In 1955, 43.3 broods per square mile were recorded as compared 
to 30.7 in 1954. There is an increase of 29 percent in the total number of broods 
produced when compared to the low 1954 figure. However, the number of broods 
is still not as high as the levels recorded for 1952 and 1953. The “pair efficiency" 
ratio or pair per brood ratio is 100:59. This compares very favorably with the 
pair per brood ratio of 100:31 for 1954. , Brood sizes were generally larger in 1955. 
Summary and Outlook 
1. Breeding pairs were down 25 percent from 1954. 
2. The number of broods produced was 29 percent greater than 
in 1954 but was not as large as production for 1952 and 1953. 
* 
3. The nesting and brood season was at least two to three weeks 
earlier than the 1954 season. It might be compared phenologically with 1952. 
