Assessing Birds of Prey as Biological Pest Control: A Comparative Study with Hunting Perches and Rodenticides on Rodent Activity and Crop Health

Rodent damage significantly affects agriculture around the world. Rodenticides sometimes can control pests but are costly, can cause secondary poisoning to nontarget wildlife, and may become less efficient over time due to bait shyness and resistance. Using wildlife as biological pest control agents, particularly barn owls (Tyto alba), has been suggested as an alternative. Barn owl nest boxes and hunting perches have been added to increase predator pressure, yet few studies have examined their effectiveness. We conducted a field study in forty-five 10x10 m² plots to compare three treatments (biological pest control by adding hunting perches, 1080 rodenticide, and control) on rodent (vole) activity and crop health (alfalfa, Medicago sativa) using unmanned aerial system (UAS) remote sensing and ground surveys. Additionally, we used 24/7 video cameras and a machine learning (YOLOv5) object detection algorithm to determine whether hunting perches increase the presence of diurnal and nocturnal raptors. Rodent activity increased during the study and did not vary among the treatments across all three treatment groups, indicating that the both the biological pest control and rodenticides did not prevent the rodent population from increasing. Moreover, the vegetation indices clearly show that the alfalfa has become increasingly damaged over time, due to rising damage caused by rodents. There were significantly more raptors in plots with hunting perches than control plots and those treated with rodenticides. Specifically, barn owls and diurnal raptors (mainly black-shouldered kites) spent 97.92% more time on hunting perch plots than rodenticide plots and 97.61% more time on hunting perch plots than control plots. The number of barn owls was positively related to vole activity, whereas the number of black-shouldered kites was unrelated to voles. Even though hunting perches effectively increased the presence and activity of diurnal and nocturnal raptors, rodent populations increased. Future research should investigate whether hunting perches can improve raptor populations and crop health in crops other than alfalfa, which is known as a particularly difficult crop to control voles in.