Make way for ducks: the effect of speed and light on mallard flight reactions during real and simulated vehicle approaches

Vehicle collisions with birds are financially costly and dangerous to humans and animals. To reduce collisions, we must better understand how birds respond to approaching vehicles. We used real and simulated vehicle approaches with mallards (Anas platyrynchos) to quantify flight behavior and probability of collision under different speed and lighting conditions. Mallards approached by a real vehicle had a delayed margin of safety; they are the first species found to use this strategy in response to vehicle approach. Nighttime lighting increased time before collision of flight in simulated trials but decreased likelihood of flight. Vehicle approaches at night might be perceived as less threatening than those during the day; alternatively, mallard visual systems might be incompatible with vehicle lighting in dark settings. Our findings suggest mallards might be unequipped to adequately respond to fast-moving vehicles and demonstrate the need for continued research into promoting avian avoidance behavior.