Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, United States of America.
PLoS One. 2019 Jul 31;14(7):e0220576. doi: 10.1371/journal.pone.0220576. eCollection 2019.
Anthropogenic noise decreases signal active space, or the area over which male bird song can be detected in the environment. For territorial males, noise may make it more difficult to detect and assess territorial challenges, which in turn may increase defense costs and influence whether males maintain territory ownership. We tested the hypothesis that noise affects the ability of male house wrens (Troglodytes aedon) near active nests to detect intruders and alters responses to them. We broadcast pre-recorded male song and pink noise on territories to simulate intrusions with and without noise, as well as to noise alone. We measured detection by how long males took to sing or approach the speaker after the start of a playback. To measure whether playbacks changed male behavior, we compared their vocal responses before and during treatments, as well as compared mean vocal responses and the number of flyovers and attacks on the speaker during treatments. Noise did not affect a male's ability to detect an intruder on his territory. Males altered their responses to simulated intruders with and without noise compared to the noise-only treatment by singing longer songs at faster rates. Males increased peak frequency of songs during intrusions without noise compared to noise-only treatments, but frequency during intruder plus noise treatments did not differ from either. When confronting simulated intruders in noise, males increased the number of attacks on the speaker compared to intruders without noise, possibly because they were less able to assess intruders via songs and relied on close encounters for information. Although noise did not affect intruder detection, noise affected some aspects of singing and aggressive responses, which may be related to the challenge of discriminating and assessing territorial threats under elevated noise.
人为噪声会减小信号活动空间，即在环境中可以探测到雄性鸟鸣的区域。对于有领地的雄性来说，噪音可能使其更难探测到并评估领地挑战，这反过来又可能增加防御成本，并影响雄性是否保持领地所有权。我们检验了以下假设，即噪音会影响活跃巢穴附近雄性画眉（Troglodytes aedon）的能力，使其无法探测入侵者，并改变它们对入侵者的反应。我们在领地播放预先录制的雄性歌曲和粉红色噪音，以模拟有噪音和无噪音的入侵，以及仅播放噪音的情况。我们通过雄性在播放开始后唱歌或接近扬声器的时间来衡量其探测能力。为了衡量播放是否改变了雄性的行为，我们比较了处理前后它们的发声反应，以及比较了处理期间的平均发声反应以及飞越扬声器和攻击扬声器的次数。噪音并没有影响雄性在其领地探测入侵者的能力。与仅播放噪音的处理相比，雄性对有噪音和无噪音的模拟入侵者的反应发生了变化，表现为唱歌时间更长，唱歌速度更快。与仅播放噪音的处理相比，雄性在没有噪音的情况下入侵时会增加歌曲的峰值频率，但在有入侵者和噪音的情况下，频率没有差异。当雄性在噪音中面对模拟入侵者时，与没有噪音的入侵者相比，它们增加了对扬声器的攻击次数，这可能是因为它们通过歌声来评估入侵者的能力降低了，只能依靠近距离接触来获取信息。尽管噪音没有影响入侵者的探测，但它影响了歌唱和攻击反应的某些方面，这可能与在噪音环境下辨别和评估领地威胁的挑战有关。
