Mulholland Tracy I, Ferraro Danielle M, Boland Kelley C, Ivey Kathleen N, Le My-Lan, LaRiccia Carl A, Vigianelli John M, Francis Clinton D
Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA 93407, USA.
Integr Comp Biol. 2018 Nov 1;58(5):967-976. doi: 10.1093/icb/icy079.
Artificial nest boxes are critical nesting sites for secondary cavity-nesting birds; however, they are often placed near roadways and in urban areas that experience noise pollution and other human-caused stressors. Recent correlative studies document both negative and positive influences of noise pollution on reproductive success. Additionally, observational studies have not determined which stage of the breeding process is most vulnerable to noise pollution-settlement, incubation, and/or provisioning. Here, we controlled for possible effects from non-random settlement and eliminated potential effects of roadways, such as collisions and chemical and light pollution, by experimentally introducing traffic noise into nest boxes after clutch initiation in two secondary-cavity nesting bird species. We found no evidence for an influence of noise on clutch size, brood size, number of fledglings, or overall nest success in western bluebirds (Sialia mexicana). In contrast, we found that ash-throated flycatcher (Myiarchus cinerascens) nests exposed to noise had lower reproductive success than quiet nests due to higher rates of abandonment at the incubation stage. Our results match recent research demonstrating that ash-throated flycatchers avoid energy-sector noise in their nest placement and, when they do nest in noise, experience stress hormone dysregulation and fitness costs. The lack of a response among western bluebirds differs from reported declines in reproductive success due to exposure to energy-sector noise; however, the absence of a response matches the response seen in other species using an in-box noise playback experiment. These results suggest that in-box noise exposure experiments may be appropriate for assessing noise impacts at the nest, and through some pathways (e.g., direct effects of noise on nestlings), but do not capture other ways in which noise can negatively affect birds during the breeding season that may ultimately cause declines in fitness. Additionally, although manipulative experiments that examine the influence of a single anthropogenic stressor on a single life stage can help reveal causal pathways, urban and other human-dominated environments are characterized by many stressors and future studies should seek to understand how noise interacts with other stressors to impact birds and other wildlife. Finally, in light of mounting evidence demonstrating declines in reproductive success due to noise, our results suggest that nest box placement near roads may be counterproductive to efforts to bolster population densities of some species.
人工巢箱是次生洞巢鸟类至关重要的筑巢地点；然而，它们常常被放置在靠近道路以及存在噪音污染和其他人为压力源的城市区域。最近的相关研究记录了噪音污染对繁殖成功率的负面和正面影响。此外，观察性研究尚未确定繁殖过程的哪个阶段最易受到噪音污染的影响——定居、孵化和/或育雏。在此，我们通过在两种次生洞巢鸟类开始产卵后，将交通噪音实验性地引入巢箱，控制了非随机定居可能产生的影响，并消除了道路的潜在影响，如碰撞、化学和光污染。我们没有发现噪音对西部蓝鸲（Sialia mexicana）的窝卵数、育雏数、雏鸟数量或总体筑巢成功率有影响的证据。相比之下，我们发现暴露于噪音中的灰喉蝇霸鹟（Myiarchus cinerascens）巢穴的繁殖成功率低于安静巢穴，原因是在孵化阶段弃巢率更高。我们的结果与最近的研究相符，该研究表明灰喉蝇霸鹟在选择筑巢地点时会避开能源行业的噪音，并且当它们在有噪音的地方筑巢时，会经历应激激素失调和适应性成本。西部蓝鸲没有反应这一情况与因暴露于能源行业噪音而导致繁殖成功率下降的报道不同；然而，没有反应这一情况与在其他物种中使用巢箱内噪音回放实验所观察到的反应一致。这些结果表明，巢箱内噪音暴露实验可能适合评估巢穴处的噪音影响，并且通过某些途径（例如，噪音对雏鸟的直接影响），但无法捕捉到噪音在繁殖季节可能对鸟类产生负面影响的其他方式，而这些方式最终可能导致适应性下降。此外，尽管研究单一人为压力源对单一生命阶段影响的操纵性实验有助于揭示因果途径，但城市和其他人类主导的环境具有多种压力源，未来的研究应设法了解噪音如何与其他压力源相互作用以影响鸟类和其他野生动物。最后，鉴于越来越多的证据表明噪音会导致繁殖成功率下降，我们的结果表明在道路附近放置巢箱可能会对提高某些物种的种群密度的努力产生适得其反的效果。
