Hole-nesting tits belonging to the family Paridae produce a hissing display that resembles the exhalatory hiss of a snake. When a predatory animal enters the nest hole of a tit, tits often hiss vigorously, while lunging their head forward and shaking their wings and tail, until the intruder retreats. We assessed the acoustic similarity between such hiss calls from 6 species of tits, snake hisses, and tit syllables used in alarm vocalizations, as well as white noise as a control. Tit hiss calls showed a high degree of similarity with snake hisses from 3 different snake families. Tit hisses had lower similarity to syllable alarm calls, suggesting convergence of tit hisses in their spectral structure. Hiss calls would only be effective in protecting nest boxes if nest predators responded to these calls. In order to test this hypothesis, we trained individual Swinhoe’s striped squirrels, Tamiops swinhoei hainanus, a common predator of egg and nestling tits, to feed at feeders in proximity to nest boxes. We compared the aversive response of squirrels to tit’s hiss calls and white noise, presented in random order. Squirrels showed a higher degree of avoidance of feeders when hiss calls were played back than when white noise was presented. In conclusion, our study suggests that hole-nesting birds have evolved convergent snake-like hiss calls, and that predators avoid to prey on the contents of nest boxes from which snake-like hisses emerge.

中文翻译：

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在繁殖的山雀中发出类似蛇的叫声

属于Paridae科的巢穴山雀会发出类似于蛇呼气嘶嘶声的嘶嘶声。当掠食性动物进入山雀的巢穴时，山雀通常会发出剧烈的嘶嘶声，同时将头向前猛冲并摇动翅膀和尾巴，直到入侵者撤退。我们评估了来自 6 种山雀、蛇嘶嘶声和用于警报发声的山雀音节的这种嘶嘶声之间的声学​​相似性，以及作为对照的白噪声。山雀嘶嘶声与来自 3 个不同蛇科的蛇嘶嘶声具有高度相似性。山雀嘶嘶声与音节警报呼叫的相似性较低，表明山雀嘶嘶声在它们的光谱结构中收敛。只有当巢穴捕食者对这些叫声做出反应时，嘶嘶声才能有效保护巢箱。为了检验这个假设，我们训练了个体 Swinhoe 的条纹​​松鼠 Tamiops swinhoei hainanus，这是一种常见的蛋和雏山雀捕食者，在巢箱附近的喂食器处觅食。我们比较了松鼠对山雀嘶嘶声和白噪声的厌恶反应，以随机顺序呈现。当播放嘶嘶声时，松鼠对喂食者的回避程度高于出现白噪声时。总之，我们的研究表明，筑巢鸟类已经进化出会聚的类似蛇的嘶嘶声，捕食者会避免捕食巢箱中出现类似蛇的嘶嘶声的内容物。以随机顺序呈现。当播放嘶嘶声时，松鼠对喂食者的回避程度高于出现白噪声时。总之，我们的研究表明，筑巢鸟类已经进化出会聚的类似蛇的嘶嘶声，捕食者会避免捕食巢箱中出现类似蛇的嘶嘶声的内容物。以随机顺序呈现。当播放嘶嘶声时，松鼠对喂食者的回避程度高于出现白噪声时。总之，我们的研究表明，筑巢鸟类已经进化出会聚的类似蛇的嘶嘶声，捕食者会避免捕食巢箱中出现类似蛇的嘶嘶声的内容物。