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Mortality During the Breeding Season

Table 12-1. Some Breeding Season (April-September) Mortality Rates of Adult Female Ducks in North America and Principal Causes of Mortalitya

Species
Habitat
Location
Method
Sample sizeb
Mortality ratec
Mortality causes d
Source
Mallard Prairie N. Dak. Fox dens
494
0.28
P, u
 Johnson and Sargeant (1977)
Mallard Prairie N. Dak. Radiotracking
235
0.19
(0.09-0.31)e
P, m
 Cowardin et al. (1985)
Mallard Forest Minn. Radiotracking
109
0.25
U, p
 Kirby and Cowardin (1986)
Mallard Prairie-parkland Alb., Man., Sask. Reward bands
16,562
0.40
U
 Blohm et al. (1987)
Black Duck Forest Maine Radiotracking
19
0.26
P
 Ringelman and Longcore (1983)
aLength of time represented in each study varies.
bNumber of fox dens examined for Mallard remains or number of adult females banded or radiotracked.
cValues are averages presented in respective source, except for Kirby and Cowardin (1986) where we excluded data for the molt and premigration period and recalculated the value from data presented. Where data for more than 1 year were provided, we present the range in annual variationin parentheses.
dMortality-cause codes are: p = predation, m = farm machinery, u = undetermined. Capital letters signify known or implied major mortality causes (>50% of mortality), and lowercase letters signify known or implied minor causes (< 50% of mortality).
eAuthors indicated the rate was probably biased low.

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