Effects of a high-power laser eye exposure on avian foraging behaviour: implications for the safety of laser bird deterrents.

To prevent human-bird conflict, lasers have been developed as nonlethal wildlife control methods despite being known to cause eye injury in humans. However, little is known about how much laser exposure can affect visually driven activities critical for survival, such as foraging. We assessed how laser exposure and its output energy affected avian visual exploratory behaviour during foraging and food consumption. We exposed house sparrows to a high-energy laser (Seabird Saver) under controlled conditions and measured within Week 1 after exposure and within Week 2 after exposure their foraging behaviour when visually locating millet seeds against a high contrast (easy task) and low contrast (difficult task) background. 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 (i.e. high acuity) visual exploration rate using more the left compared to the right eye, particularly with increasing laser energy levels. Laser exposure increased pecking rates and seed consumption rates both within Week 1 and within Week 2 after exposure. This result is consistent with variations in body mass, which decreased markedly right after laser exposure, but animals recovered their pre-exposure weight over a few days. Our findings suggest that exposure to a high-energy laser (Seabird Saver) can alter visual exploratory behaviour in the context of foraging and influence foraging effort and food consumption rates. We discuss the implications for the use of lasers as wild bird deterrents at airports, landfills, fisheries, etc.