Effects of Laser Exposure on Avian Foraging Behavior

Abstract

To prevent human-bird conflict, lasers have been developed as nonlethal control methods despite being known to cause eye injury and visual function deficits in humans under certain conditions. Determining the extent to which laser exposure is also an ocular hazard for birds is important because birds rely heavily on vision for activities critical to their survival, like foraging. The purpose of this study was to assess how laser exposure and the energy of exposure affects avian visual exploratory behavior for the purpose of foraging, as well as food consumption. We recorded the food visual exploratory behavior and food consumption of 40 house sparrows using foraging trials where they were tasked with finding millet seeds against a high contrast (easy task) and low contrast (difficult task) background according to their contrast sensitivity. After a baseline assessment of behavior, each bird was exposed to a unique laser energy and participated in the foraging trials again within week 1 after exposure and within week 2 after exposure. We found that house sparrows arrived at the food patch quicker and decreased their use of binocular vision within week 1 after exposure compared to before exposure. Within week 1 and within week 2 after exposure, birds changed their rates of scanning depending on the difficulty of the foraging task. They also developed laterality by increasing foveal vision rate using the left eye compared to the right. This laterality was even more pronounced in birds exposed to higher energy levels. Although laser exposure did not affect the overall amount of food birds consumed, they increased pecking rates and seed consumption rates both within week 1 and within week 2 after exposure. This study was the first controlled experiment examining the effects of laser exposure and laser energy on avian behavior. The evidence suggests that laser exposure can alter visual exploratory behavior in the context of foraging and influence foraging effort and food consumption rates. These results have important implications for the use of lasers as wild bird deterrents.