1.07 (mallard index) : 1.00 (mallard rating) = 
1.19 (black duck index) : xX 
or 1.15 = 1.07 (corrected rating for black ducks) 
1.07 
Thus, black ducks have 4 vulnerability rating that is 1.07 
times as great as for mallards on the Upper Mississippi. 
The same formula was used for all species, for all areas 
and all periods, and tables 23 and 24 were worked out. (See 
pages 38 and 39.) 
By assigning these vulnerability ratings it is possible to 
not only compare other species to mallards, but also the compara- 
tive vulnerability between any species can be determined. For 
example, gadwall have a rating of 1.01 and blue-winged teal a 
rating of 2.01. Therefore, blue-winged teal are twice as vulner- 
able under hunting conditions in this area as are gadwall. Scaup 
have a rating of 0.21 compared with green-winged teal with a rat- 
ing of 3.5/7. Thus, under conditions here, green-winged teal are 
17 times as vulnerable as are scaup. This, of course, would not 
be true in an area where point or open-river shooting predominated, 
but it does apply to this area where most of the shooting is done 
in the marshes and mostly from blinds. 
Tables 24 and 25 compare the percentage composition of the 
population and the checked kill on the Upper Mississippi Refuge 
for the opening week of the hunting season and for the entire 
season. Note that the tables are broken down into three segments: 
(1).the period 1953 thru 1958 when the latest opening was October 
3; (2) the period 1959 and 1960 when the season opened on Octo- 
per 7; and (3) the entire period 1953 thru 1960. This was done 
to illustrate the difference in both populations and harvest that 
occur within the various segments. An opening delayed only 1 
week makes a tremendous difference in the composition, especially 
with blue-winged teal. It will be noted that with the season 
opening between October 1 and 3, blue-wings averaged 27.87% of 
the population present and 48.31% of the checked kill. With the 
opening delayed to October 7, this species made up only 9.35% of 
the population and 28.71% of the checked kill. Oddly enough, in 
the period 1953 thru 1958, with more blue-wings present in both 
the population and the checked kill, they had a vulnerability 
rating of 1.78, while from 1959 thru 1960 the rating was 3.07. 
Thus, although fewer blue-wings were present in the latter 2 years, 
those which were present were taken at a much higher rate per unit 
of population than for the 1953-58 seasons which had higher numbers 
present in both the population and the checked kill. 
37 
