Billions of birds fatally collide with human-made structures each year. This source of mortality is a significant threat to bird populations and poses serious challenges for human industries. Efforts to reduce collisions have largely centered on making structures more visible to birds but have been met with limited success. Solutions addressing the environmental context of hazards and the behavioral ecology of at-risk birds offer more tangible results. Birds have largely evolved without tall human-made structures in their flight path. Consequently, avian perception and behavior may not be suitably primed to detect these evolutionarily novel hazards. Our previous work in captive settings has shown that conspicuous acoustic signals may aid in drawing the attention of flying birds to potential collision hazards. We consequently aimed to corroborate these findings in a field setting. We projected acoustic signals into air space surrounding communication towers and quantified differential movement patterns of flying birds as indicators of collision avoidance behavior. We employed a video-graphic 3-dimensional modeling technique to analyze these bird flight movements. We also worked towards identifying which specific elements of acoustic signals elicit more collision-avoidance behavior. Tests of differing types of acoustic signals in our captive and field-based experiments allowed for comparisons of the efficacy of signal types in influencing avian flight behavior and potential collision risk.
Results/Conclusions
Preliminary results from our field studies indicate that birds interacting with structures under sound treatment conditions experienced a 30% reduction in collision risk compared to control conditions. These results vary by geographical location and weather conditions, thus reinforcing an appreciation of the context-dependent nature of collisions. Our work towards characterizing conspicuous elements of acoustic signals will offer valuable insights to the field of avian sensory ecology, which currently lacks ecologically relevant measures of avian auditory sensitivity. Our derived metrics quantify bird flight behaviors, and associated collision risks, in a real-time manner previously unattainable in traditional measures. This approach offers a compelling novel method for rapidly evaluating collision risk and mitigation techniques. Findings from our studies will inform the field of avian sensory ecology and assess the use of acoustic signals in collision mitigation measures.