Density estimates are important to investigations of population dynami
cs and the effectiveness of management activities. Methods currently u
sed to estimate density of breeding female Mallards (Anas platyrhyncho
s) on localized study areas were derived ad hoc and have never been va
lidated. The accuracy of ad-hoc estimates was tested by comparing them
to mark-resight estimates of female density During spring 1993, 61 fe
males were color- and radio-marked in southcentral Saskatchewan, and d
ensity was estimated via ad-hoc and mark-resight methods using data fr
om four surveys. The assumptions and minimum data requirements of the
mark-resight technique were met, and a reliable benchmark estimate of
density was developed using data from the second survey (3.7 females/k
m(2), SE = 0.8). Ad-hoc and mark-resight estimates were significantly
different (P = 0.046), with the ad-hoc estimate being greater by 1.5 f
emales/km(2). For many research and monitoring applications, this leve
l of error may be inconsequential, and the ad-hoc estimator, which is
more easily applied than the mark-resight estimator, may be adequate.
The mark-resight estimator can be used to provide more accurate estima
tes with measured precision but requires that large samples of females
be color- and radio-marked, monitored and resighted.