Black ducks banded at McGinnis Slough, table 6, had mortality losses that totaled 94.2 
per cent through year-class 3-4, while mallards banded there had losses amounting to 92.1 per 
cent through the same year-class. The average of yearly mortality rates through year-class 4-5 
was 53.7 per cent for the black duck, 46.4 per cent for the mallard. 
Blue-winged teals banded at McGinnis Slough, table 7, had higher mortality losses than 
either mallards or black ducks banded there. The average of yearly mortality rates for the blue- 
wings was 57.1 per cent, more than 3 per cent higher than for black ducks. Although there was 
no well-defined yearly trend in the mortality rates of the mallards and black ducks, the mortality 
rate of the blue-winged teals increased with each successive year-class, 
LONGEVITY. --Longevity, as used here, is the life expectancy of a duck after banding. 
Longevity research does not provide information essential for evaluating population mechanics, 
but it may provide figures readily comprehended by the layman. Because some investigators 
have used them, we include longevity figures for mallards for comparison with the figures for 
‘other species. 
There is a difference in longevity data as obtained by mean (average) and by median 
(mid-point) figures, table 8. This difference occurs because a few individuals lived a dispropor- 
Table.8.--Expectation of further life after September 1 in year of banding by mallards 
banded at Lake Chautauqua, 1939-1944, as determined from mean and median calculations. 
Life Expectancy in Years 
Adult Juvenile Adult Male and 
Statistic Used Male Male 
Juvenile Male 
Mean (average)--------- 1.79 WA?) 
Median (mid- 
pozalish Aol itd 0.23 
tionately large number of years. Because the median figures are more precise measurements 
Female 
of population longevity, we believe they should be used in measurements of longevity, particularly 
in comparisons with other species. 
According to figures presented by Addy (1945) the longevity of the black duck in New 
England is slightly less than that of the mallard in Illinois. Addy found that the average life 
span of black ducks after banding at three stations in Massachusetts was 1.17, 1.29, and 1.49 
years. In Illinois the life span of mallard drakes averaged 1.56 years and that of hens 1.38 
vears in the years of this study. 
YEARLY HUNTER-BAG. --Yearly hunter-bag losses for mallards are given in tables 
9 and 10, for black ducks in table 11, and for blue-winged teals in table 12. These bag figures 
involve only those ducks from which the bands were recovered in the year of banding. In the 
case of mallards and black ducks, the figures are corrected to compensate for banding during 
the hunting season mid-way down the flyway. 
le 
