Local movements of farmed‐released versus wild mallards Anas platyrhynchos in fall

Abstract

Releasing farmed mallards into the wild is a common practice in wildlife management worldwide, involving millions of birds annually, and is mainly carried out to increase hunting opportunities. Ringing and previous research show that released mallards have low survival also outside the hunting season, and that survivors may compromise migration habits, morphology, and adaptations of the wild population. Detailed local movements of released mallards have not been studied before, despite the importance of spatiotemporal patterns for understanding the impact of releases and their utility for hunting. We studied local movements in August–October of 11 wild and 44 released mallards caught in the same wetland in southern Sweden and provided with GPS tags. Wild mallards moved longer distances than farmed, over the whole diel cycle, as well as during three out of four separate periods of the day (dawn, day, and dusk). Mallards of both origins moved the longest distances during dusk and dawn, and the shortest during the night. Males and females did not differ significantly in distance moved, regardless of origin (wild versus farmed). Our study demonstrates large differences in spatiotemporal movement patterns between wild and farmed mallards. The typical day of wild mallards included movements between wetlands in the landscape, likely to foraging sites known from previous experience. However, wild mallards frequently returned to the study wetland, probably attracted by supplementary bait. On the other hand, farmed mallards seldom left the study wetland, despite the possibility of accompanying wild birds to other sites. The sedentary behavior of farmed mallards and the fact that wild birds come to join them are both beneficial for hunting purposes. Limited movements of farmed mallards, together with their low survival, could also be positive as they limit hybridization between wild and farmed mallards, as well as dispersal of nutrients.