EVALUATION OF METHODS FOR ESTIMATING DENSITY OF BREEDING FEMALE MALLARDS

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.