Human activity around the globe is a growing source of selection pressure on animal behavior and communication systems. Some animals can modify their vocalizations to avoid masking from anthropogenic noise. However, such modifications can also affect the salience of these vocalizations in functional contexts such as competition and mate choice. Such is the case in the well-studied Nuttall's white-crowned sparrow (Zonotrichia leucophrys nuttalli), which lives year-round in both urban San Francisco and nearby rural Point Reyes. A performance feature of this species' song is salient in territorial defense, such that higher performance songs elicit stronger responses in simulated territorial intrusions; but songs with lower performance values transmit better in anthropogenic noise. A key question then is whether vocal performance signals male quality and ability to obtain high quality territories in urban populations. We predicted white-crowned sparrows with higher vocal performance will be in better condition and will tend to hold territories with lower noise levels and more species-preferred landscape features. Because white-crowned sparrows are adapted to coastal scrub habitats, we expect high quality territories to contain lower and less dense canopies, less drought, more greenness, and more flat open ground for foraging. To test our predictions, we recorded songs and measured vocal performance and body condition (scaled mass index and fat score) for a set of urban and rural birds (N = 93), as well as ambient noise levels on their territories. Remote sensing metrics measured landscape features of territories, such as drought stress (NDWI), greenness (NDVI), mean canopy height, maximum height, leaf area density (understory and canopy), slope, and percent bare ground for a 50 m radius on each male territory. We did not find a correlation between body condition and performance but did find a relationship between noise levels and performance. Further, high performers held territories with lower canopies and less dense vegetation, which are species-preferred landscape features. These findings link together fundamental aspects of sexual selection in that habitat quality and the quality of sexually selected signals appear to be associated: males that have the highest performing songs are defending territories of the highest quality.

中文翻译：

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地域质量预测跨越城乡梯度的鸟类声乐表现

全球的人类活动是对动物行为和交流系统产生选择压力的一个越来越大的来源。一些动物可以修改它们的发声以避免被人为噪音掩盖。然而，这种修改也会影响这些发声在竞争和择偶等功能环境中的显着性。研究良好的纳托尔白冠麻雀（Zonotrichia leucophrys nuttalli）就是这种情况，它全年生活在旧金山市区和附近的雷耶斯角农村。该物种歌曲的一个表现特征在领土防御方面很突出，因此在模拟领土入侵中，表现力越高的歌曲会引起更强的反应；但性能值较低的歌曲在人为噪声中的传输效果更好。那么一个关键问题是声乐表演是否表明男性的素质和在城市人口中获得高质量领地的能力。我们预测具有较高声音表现的白冠麻雀将处于更好的状态，并且倾​​向于占据噪音水平较低和更多物种偏好的景观特征的领土。由于白冠麻雀适应沿海灌木栖息地，因此我们预计高质量的领地将包含更低且密度更低的树冠、更少的干旱、更多的绿色和更平坦的开阔地供觅食。为了测试我们的预测，我们录制了一组城市和乡村鸟类（N = 93）的歌曲并测量了声音表现和身体状况（缩放质量指数和脂肪分数），以及它们领土上的环境噪音水平。遥感指标测量领土的景观特征，例如干旱胁迫 (NDWI)、绿度 (NDVI)、平均冠层高度、最大高度、叶面积密度（林下和冠层）、坡度和每个雄性领地 50 m 半径内的裸地百分比。我们没有发现身体状况和表现之间的相关性，但确实发现了噪音水平和表现之间的关系。此外，表现出色的地区拥有较低的树冠和较不密集的植被，这是物种偏好的景观特征。这些发现将性选择的基本方面联系在一起，因为栖息地质量和性选择信号的质量似乎相关：拥有最高表现歌曲的雄性正在捍卫最高质量的领土。每个男性领土上半径 50 m 的裸地百分比。我们没有发现身体状况和表现之间的相关性，但确实发现了噪音水平和表现之间的关系。此外，表现出色的地区拥有较低的树冠和较不密集的植被，这是物种偏爱的景观特征。这些发现将性选择的基本方面联系在一起，因为栖息地质量和性选择信号的质量似乎相关：拥有最高表现歌曲的雄性正在捍卫最高质量的领土。每个男性领土上半径 50 m 的裸地百分比。我们没有发现身体状况和表现之间的相关性，但确实发现了噪音水平和表现之间的关系。此外，表现出色的地区拥有较低的树冠和较不密集的植被，这是物种偏好的景观特征。这些发现将性选择的基本方面联系在一起，因为栖息地质量和性选择信号的质量似乎相关：拥有最高表现歌曲的雄性正在捍卫最高质量的领土。表现出色的地区拥有较低的树冠和较不密集的植被，这是物种偏爱的景观特征。这些发现将性选择的基本方面联系在一起，因为栖息地质量和性选择信号的质量似乎相关：拥有最高表现歌曲的雄性正在捍卫最高质量的领土。表现出色的地区拥有较低的树冠和较不密集的植被，这是物种偏爱的景观特征。这些发现将性选择的基本方面联系在一起，因为栖息地质量和性选择信号的质量似乎相关：拥有最高表现歌曲的雄性正在捍卫最高质量的领土。