Biology Department, William & Mary, Williamsburg, Virginia, United States of America.
Department of Biological and Environmental Sciences, Longwood University, Farmville, Virginia, United States of America.
PLoS One. 2021 Apr 28;16(4):e0249826. doi: 10.1371/journal.pone.0249826. eCollection 2021.
Billions of birds fatally collide with human-made structures each year. These mortalities have consequences for population viability and conservation of endangered species. This source of human-wildlife conflict also places constraints on various industries. Furthermore, with continued increases in urbanization, the incidence of collisions continues to increase. Efforts to reduce collisions have largely focused on making structures more visible to birds through visual stimuli but have shown limited success. We investigated the efficacy of a multimodal combination of acoustic signals with visual cues to reduce avian collisions with tall structures in open airspace. Previous work has demonstrated that a combination of acoustic and visual cues can decrease collision risk of birds in captive flight trials. Extending to field tests, we predicted that novel acoustic signals would combine with the visual cues of tall communication towers to reduce collision risk for birds. We broadcast two audible frequency ranges (4 to 6 and 6 to 8 kHz) in front of tall communication towers at locations in the Atlantic migratory flyway of Virginia during annual migration and observed birds' flight trajectories around the towers. We recorded an overall 12-16% lower rate of general bird activity surrounding towers during sound treatment conditions, compared with control (no broadcast sound) conditions. Furthermore, in 145 tracked "at-risk" flights, birds reduced flight velocity and deflected flight trajectories to a greater extent when exposed to the acoustic stimuli near the towers. In particular, the 4 to 6 kHz stimulus produced the greater effect sizes, with birds altering flight direction earlier in their trajectories and at larger distances from the towers, perhaps indicating that frequency range is more clearly audible to flying birds. This "acoustic lighthouse" concept reduces the risk of collision for birds in the field and could be applied to reduce collision risk associated with many human-made structures, such as wind turbines and tall buildings.
每年都有数十亿只鸟类因与人为结构相撞而致命。这些死亡率对物种的生存和保护濒危物种都有影响。这种人为与野生动物的冲突也对各种行业造成了限制。此外，随着城市化的持续发展，碰撞事件的发生率还在继续增加。减少碰撞的努力主要集中在通过视觉刺激使结构对鸟类更具可见性上，但收效有限。我们研究了通过声音信号与视觉线索相结合的多模态方法，以减少鸟类与空旷地带高大结构的碰撞。以前的工作表明，声音和视觉线索的结合可以降低笼养飞行试验中鸟类的碰撞风险。扩展到野外试验，我们预测新的声音信号与高大通讯塔的视觉线索相结合，将降低鸟类与通讯塔碰撞的风险。我们在弗吉尼亚州大西洋迁徙飞行路线上的地点，在高大通讯塔前播放两个可听频率范围（4 至 6 kHz 和 6 至 8 kHz），并观察鸟类在塔周围的飞行轨迹。与对照（无广播声音）条件相比，在声音处理条件下，我们记录到周围塔的鸟类总活动率降低了 12-16%。此外，在 145 次跟踪的“高危”飞行中，当鸟类暴露在塔附近的声音刺激下时，它们会更大程度地降低飞行速度并改变飞行轨迹。特别是 4 至 6 kHz 的刺激产生了更大的效果，鸟类更早地改变了飞行方向，与塔的距离也更大，这可能表明该频率范围对飞行鸟类的可听度更高。这种“声灯塔”概念降低了鸟类在野外碰撞的风险，可应用于降低与许多人为结构（如风力涡轮机和高楼大厦）相关的碰撞风险。
