DETERMINING MORTALITY RATES 
A start has been made toward evaluating lead poisoning losses among wild, unpenned ducks swal- 
lowing only one shot pellet. The difference in second-year band returns between an undosed group and 
a group dosed with one shot pellet each should represent the mortality rate caused by one shot pellet 
per bird if no compensating adjustments are involved. 
A total of 113 bands was reported taken during the 1950 season from 1,119 wild mallard drakes 
used in the 1949 experimental release of dosed and undosed birds. Fifty-five of the 113 were from the 
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RRR [KK Fig. 13. -- Percentage of birds in five groups of 
Netecer I etecer 
banded wild mallards that were reported killed 
(by return of bands) in year of banding. In 1949 
NUMBER OF PELLETS 
Fig. 12.-- Percentage of wild duck gizzards con- 
taining various numbers of commercial shot pel- 
lets. Data are for 957 gizzards that contained shot 
in a total number of 18,115 gizzards collected in 
recent years, fall and early winter. 
SwiGh= 
about 560 mallards were banded in each of two 
groups, one group carrying no lead and the other 
one no. 6 pellet to each bird. In 1950, about 390 
were banded in each of three groups, one group 
carrying no lead, one group one no. 6 pellet to 
each bird, and one group two no. 6 pellets to 
each bird. 
