Effects of spinning-wing decoys on flock behavior and hunting vulnerability of mallards in Minnesota

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). Accordingly, we conducted 219 experimental hunts to evaluate hunting vulnerability of mallards to SWDs during the 2002 duck season in Minnesota. During each hunt, we tested 2 SWD treatments: 1) SWDs turned OFF (control), and 2) SWDs turned ON (experimental) during alternate 15-minute sampling periods that were separated by 5-minute buffer periods. We found that mallard flocks (≥1 duck) were 2.91 times more likely to respond (i.e., approach within 40 m of hunters), and sizes of responding mallard flocks were 1.25 times larger, on average, when SWDs were turned ON than OFF. Mallards killed/hour/hunter/hunt averaged 4.71 times higher (P