Condition bias of hunter-shot mallards (Anas platyrhynchos)

Abstract

We tested the hypothesis that hunters using decoys disproportionately shot ducks in poor condition. We compared weights of 316 hunter-shot mallards (Anas platyrhynchos) with those of 156 mallards we collected by jump or pass shooting at a roost. Data were subdivided by age, sex, and sampling period. In support of the hypothesis, in 11 of 12 comparisons, hunter-shot ducks weighed less than ducks collected at the roost and those differences were significant for five of the seven largest samples. Also consistent with the hypothesis, weights of hunter-shot birds were less variable than weights of birds collected at the roost in 9 of 12 comparisons. Through the fall collection period, the mean weight of ducks shot by hunters remained constant, while the weight of ducks sampled at the roost increased by 5.4%. Our results support the argument that caution must be exercised when using data from hunter-shot waterfowl for management programs based on band-recovery analysis or for any other purpose for which a condition bias could influence the interpretation of those data.