Spring and Summer Age Separation Techniques for the Mallard

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Abstract
A quantitative technique was developed to distinguish adult from yearling A. platyrhynchos during the breeding season using wing feather measurements of 423 fall shot birds. Mean feather measurements of adults of both sexes were larger than those of immatures (yearlings). The best measurement for separating ages in both sexes was vane width at the tip of greater secondary covert 5. Four and 5 variables were required to correctly classify the age of 91 and 95% of the hens and drakes, respectively. Wing feathers were measured on 50 known age wild mallards captured in southern Manitoba [Canada] during spring and summer, 1975-1979. All 4 of the yearlings and 22 (88%) of the adults captured in 1975-1976 were correctly classified using discriminant functions developed from wing measurements of fall-shot birds. Use of the qualitative age characters, covert shape and primary coloration, resulted in the correct classification of all known-age wild yearlings and 91% of the known-age wild adults. Covert wear and bill spotting were poor indicators of age for breeding mallards.

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