Department of Entomology and Wildlife Ecology, University of Delaware, Newark, DE 19716, USA.
Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, 615 E. Peabody Drive, MC-650, Champaign, IL 61820, USA.
Integr Comp Biol. 2021 Oct 4;61(3):1216-1236. doi: 10.1093/icb/icab154.
Artificial light at night (ALAN) on tall or upward-pointed lighting installations affects the flight behavior of night-migrating birds. We hypothesized that common low-rise lights pointing downward also affect the movement of nocturnal migrants. We predicted that birds in flight will react close to low-rise lights, and be attracted and grounded near light sources, with a stronger effect on juveniles during their autumn migration. We conducted a controlled longitudinal experiment with light-emitting diode floodlights and considered nearby structures that turn on lights at night. We analyzed 1501 high-resolution 3D nocturnal flight paths of free-flying migrants and diurnally captured 758-2009 birds around experimental lights during spring and autumn 2016, and spring 2017. We identified change points along flight paths where birds turned horizontally or vertically, and we considered these indicative of reactions. Flight paths with and without reactions were generally closer to our experimental site in spring than in autumn when the lights were on. Reactions were up to 40% more likely to occur in autumn than in spring depending on the threshold magnitude of turning angle. Reactions in spring were up to ∼60% more likely to occur at ∼35 m from the lights than at >1.5 km. In autumn, some vertical reactions were ∼40% more likely to occur at ∼50 m from the lights than at >2.2 km. Interactions between distance to lights and visibility or cloud cover were consistent with known effects of ALAN on nocturnal migrants. Under poor visibility, reactions were up to 50% more likely to occur farthest from structures in spring, but up to 60% more likely to occur closest to lights in autumn. Thus, the effects of ALAN on night-migrating land birds are not limited to bright lights pointing upward or lights on tall structures in urban areas. Diurnal capture rates of birds were not different when lights were on or off for either season. To our knowledge, this is the first study to show that low-rise lights pointing downward affect night-migrating birds. Although the interpreted reactions constitute subtle modifications in the linearity of flight paths, we discuss future work that could verify whether the protection of nocturnal migrants with lights-out programs would have greater impact if implemented beyond urban areas and include management of low-rise lights.
夜间人工照明（ALAN）在高大或向上指向的照明装置上会影响夜间迁徙鸟类的飞行行为。我们假设常见的指向下方的低矮灯也会影响夜间迁徙的候鸟的活动。我们预测，飞行中的鸟类会在靠近低空灯的地方做出反应，并在光源附近被吸引和着陆，对于秋季迁徙的幼鸟来说，这种影响会更强。我们进行了一项使用发光二极管泛光灯的对照纵向实验，并考虑了夜间开灯的附近建筑物。我们分析了 2016 年春季和秋季以及 2017 年春季自由飞行候鸟的 1501 条高分辨率 3D 夜间飞行路径，以及在实验灯周围夜间和白天捕获的 758-2009 只鸟类。我们在飞行路径上识别出鸟类水平或垂直转弯的变化点，并认为这些变化点表明鸟类做出了反应。有反应的飞行路径通常比秋季的飞行路径更靠近实验点，而秋季的灯是开着的。根据转弯角度的阈值大小，秋季的反应比春季更有可能发生，反应的可能性高达 40%。春季的反应在距离灯约 35 米处比在距离灯大于 1.5 公里处更有可能发生约 60%。秋季，一些垂直反应在距离灯约 50 米处比在距离灯大于 2.2 公里处更有可能发生约 40%。距离灯的距离与可见度或云覆盖之间的相互作用与 ALAN 对夜间迁徙候鸟的已知影响一致。在能见度差的情况下，春季，距离建筑物最远的地方发生反应的可能性增加了 50%，而秋季，距离灯最近的地方发生反应的可能性增加了 60%。因此，ALAN 对夜间迁徙的陆地鸟类的影响不仅限于指向天空的明亮灯光或城市地区的高塔上的灯光。对于两个季节，无论是开灯还是关灯，鸟类的日间捕获率都没有差异。据我们所知，这是第一项表明指向下方的低矮灯也会影响夜间迁徙鸟类的研究。虽然解释的反应构成了飞行路径线性的微妙变化，但我们讨论了未来的工作，如果在城市地区之外实施并包括对低矮灯的管理，熄灯计划对保护夜间迁徙的候鸟是否会产生更大的影响。
