Variation in diurnal and nocturnal movements distances revealed in wintering dabbling ducks in the Mississippi Alluvial Valley

Abstract

Movement of waterfowl during winter is central to resource acquisition and mortality avoidance, despite the imminent risk to survival and overall fitness induced by hunting disturbance and energy expenditure. Weather and other environmental conditions may influence movement by altering resource needs, in which ducks must balance the trade‐offs of resource acquisition and risk management. We compared how environmental factors influenced total daily diurnal and nocturnal movement distances of three dabbling duck species wintering in the Mississippi Alluvial Valley. We estimated total daily diurnal and nocturnal movement distances of green‐winged teal (Anas crecca; n = 51), American wigeon (Mareca americana; n = 38), and mallards (Anas platyrhynchos; n = 31) using backpack transmitters during the winter period of February–November 2020–2021 and 2021–2022. We used linear mixed effects models to model the influence of weather, hunt season, day of season, and sex on total diurnal and nocturnal movement distances by species. Green‐winged teal moved 7.7% further during the nocturnal period (x̅ = 3.38 km; SE = 0.32; p < 0.001) than during the diurnal period (x̅ = 3.13 km SE = 0.10), while American wigeon and mallards moved 36.6% (x̅ = 4.95 km; SE = 0.20; p < 0.001) and 28.1% (x̅ = 4.39 km; SE = 0.23; p < 0.001) further during the diurnal period than the nocturnal period (x̅ = 3.42 km, SE = 0.28 and x̅ = 3.31 km, SE = 0.22), respectively. Fine‐scale movement distances during the diurnal period were weakly associated with environmental covariates for all species. Conversely, moon illumination influenced nocturnal movement distances for all species. Nightly movement distances of mallards increased by 2.1 times from new to full moon during the hunting season. Conversely, there were no changes in nocturnal movement distance during pre‐hunt and post‐hunt periods when hunting disturbance was absent. In the face of intensifying environmental pressures on movement patterns in dabbling duck populations, this research demonstrates a behavioral response to moon illumination as a mechanism for moving about the landscape for resource acquisition in the presence of human disturbances that induce risk, such as hunting.