82 

** Stratum ''B" data for 1951 are not corrected for absent hens, 
and show a lower population than would treatment 
Similar to the four subsequent years. | 
Table VI. - Percent Lone Males,* Southern Manitoba, May Aerial Survey. 
% Lone Males % Lone Males , % Lone Males In 
Year In Stratum A In Stratum B Stratum A&B 
1951 45.1% 68.0% 51.0% 
1952 49.4% 37.6% 45.9% 
1953 . 45.4% 51.3% 47.9% 
1954 56. 3% 67.7% 61.1% 
1955 65. B% 77.1% 72.0% 

* The ratio of drakes without hens to all drakes seen. 
The factors of population, water and percent lone males may be 
combined in a forecast index as shown in Figure l. Each factor is given an 
appropriate value, further corrected for additional weighting. The sum of these 
factors is the forecast index. The average index is the sum of the average of 
each factor, rather than the average of the values or indices. 
In arriving at the index, the greatest weight is given to the spring 
population. Water in Manitoba is generally not a critical item and is often 
super-abundant. Thus, water has been given a low value which has very little 
effect on the index above 20 ponds per square mile. The lone male is given 
intermediate weight. On this basis, the 1955 forecast index is 22 percent above 
the average and 14 percent above 1955. 
Production 
The 1955 aerial production survey was run from July 4 to 12 in 
Stratum "A" and July 10 to 14.in Stratum "'B". Due to the early phenology of the 
1955 season, this was perhaps somewhat later than optimum. However, the 
earliest significant hatch occurred between May 25 and June 1. Allowing 46 and 
52 days for pintails and mallards respectively ~ to reach flying age, the first 
hatch should not have been flying before July 10 and July 16 for the two species. 
——_— —— ee ee ee 
_ 
Gollop, J. B, and Marshall, W. H., 
1954 - A Guide to Ageing Duck Broods in the Field. Miss. Flyway 
Council Tech. Section Bulletin. 
