Effects of noise from four types of extractive energy infrastructure on song features in Savannah Sparrows (Passerculus sandwichensis)

Human activities change the acoustic environment in many setting around the world. These changes are complex, as different anthropogenic sound sources create different acoustic profiles; therefore, some sound sources may have greater impacts on wildlife than others. Animals may adapt to these altered acoustic environments by adjusting their vocalizations. In the case of bird song, this may be achieved by adjusting the whole song, which may preserve the spectral and temporal relationships between successive syllables, or adjusting components (syllables) within the song. Determining which syllables are adjusted may help elucidate the mechanisms, benefits, and limitations to song plasticity. We examined effects of conventional industrial infrastructure used to extract shallow natural gas and petroleum (natural gas compressor stations, generator-powered oil well pumpjacks, power grid-powered oil well screw pumps, and generator-powered oil well screw pumps), compared with quiet control sites, on 15 variables describing the acoustic properties of whole songs and syllables in Savannah Sparrows (Passerculus sandwichensis). Changes in acoustic properties varied with syllable and infrastructure type: most effects occurred at generator-powered screw pump sites, the loudest type of infrastructure that we studied. We found no effects of infrastructure on whole song variables, but song minimum frequency increased with ambient background noise. We found differing effects of infrastructure types on individual syllable types, with alterations in frequencies, tonality and syllable duration. This suggests that some syllables may be more plastic in their response than others, which may allow Savannah Sparrows to adapt their communication in altered acoustic environments.全球诸多生态场景中，人类活动均会改变区域声环境。这类变化具有复杂性：不同人为声源会形成各异的声学特征谱，因此部分声源对野生动物的影响程度可能高于其他声源。动物可通过调整发声行为来适应改变后的声环境。以鸟类鸣唱为例，此类适应可通过两种路径实现：一是调整完整鸣唱结构，此举可保留连续音节（syllable）间的频谱与时域关联；二是调整鸣唱内部的组成单元——音节。明确哪些音节发生了调整，有助于阐明鸣唱可塑性的内在机制、优势与局限。本研究以沙鹀（Passerculus sandwichensis）为研究对象，选取15项描述其完整鸣唱与音节声学特性的变量，对比分析了常规浅层天然气、石油开采工业基础设施（包括天然气压缩机站、发电机驱动式油井抽油机、电网驱动式油井螺杆泵以及发电机驱动式油井螺杆泵）与安静对照位点对上述变量的影响效应。声学特性的变化因音节类型与基础设施类型而异：本研究中影响效应最显著的为发电机驱动式油井螺杆泵位点，该类设施为本研究涉及的最响亮的工业基础设施。研究未发现基础设施对完整鸣唱变量产生显著影响，但鸣唱最低频率随环境背景噪声升高而增加。同时发现不同基础设施类型对单个音节类型的影响存在差异，具体表现为音节的频率、调谐性（tonality）以及持续时间发生改变。这表明部分音节的响应可塑性可能高于其他音节，这或许使沙鹀能够在改变后的声环境中调整其通讯交流行为。