Master of Science (MS)


Renewable Natural Resources

Document Type



Waterfowl managers in Minnesota and other states are concerned that increased kill rates associated with the use of spinning-wing decoys (SWDs) may negatively affect local breeding populations of mallards (Anas platyrhynchos). I conducted 219 experimental hunts to evaluate hunting vulnerability of mallards to SWDs during the 2002 duck-hunting season in Minnesota. Following experimental hunts, I asked volunteer hunters to complete post-hunt questionnaires to document their hunting experience, and their use and opinions of SWDs. Finally, I used stable isotope methodology to determine natal origins of HY mallards killed during experimental hunts. I found that mallard flocks (≥1 duck) were 2.91 times more likely to respond (i.e., approached within 40 m of hunters) when SWDs were turned ‘ON’. Sizes of responding mallard flocks were 1.25 times larger, on average, when SWDs were turned ‘ON’ than ‘OFF’. Mallards killed/hr/hunter/hunt averaged 4.71 times higher (P < 0.05) when SWDs were turned ‘ON’ than ‘OFF’. More HY and AHY mallards were killed when SWDs were turned ‘ON’ than ‘OFF’; however, AHYs were relatively less likely than were HYs to be killed with SWDs turned ‘ON’. Based on my stable isotope analysis, more local and migrant HY mallards were killed by hunters when SWDs were turned ‘ON’ than ‘OFF’, but local HY mallards were not relatively more likely than were migrant HY mallards to be killed by hunters using SWDs in Minnesota. I found no evidence that SWDs reduced crippling nor allowed hunters to harvest relatively more drakes than hens. I estimated that if 46% and 79% of Minnesota hunters used SWDs in 2000 and 2002, respectively, Minnesota mallard harvest would increase by factors of 2. However, increasing use of SWDs may result in a partial re-distribution of annual mallard harvests if naïve ducks are harvested upon initial exposures to SWDs, and those ducks that survive migrations to wintering areas become habituated to SWDs, as suggested by my results. My study was confined to a single hunting season in Minnesota, and thus, did not assess whether vulnerability of mallards to hunters using SWDs varies among years or geographically. A multi-year, flyway-wide study is needed to make stronger and more rigorous inferences regarding potential changes in annual harvest rates of mallards due to increasing use of SWDs by hunters in North America.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Alan D. Afton