Geographic differences in vocalizations provide strong evidence for animal culture, with patterns likely arising from generations of social learning and transmission. Most studies on the evolution of avian vocal variation have predominantly focused on fixed repertoire, territorial song in passerine birds. The study of vocal communication in open-ended learners and in contexts where vocalizations serve other functions is therefore necessary for a more comprehensive understanding of vocal dialect evolution. Parrots are open-ended vocal production learners that use vocalizations for social contact and coordination. Geographic variation in parrot vocalizations typically take the form of either distinct regional variations known as dialects or graded variation based on geographic distance known as clinal variation. In this study, we recorded monk parakeets (Myiopsitta monachus) across multiple spatial scales (i.e., parks and cities) in their European invasive range. We then compared calls using a multilevel Bayesian model and sensitivity analysis, with this novel approach allowing us to explicitly compare vocalizations at multiple spatial scales. We found support for founder effects and/or cultural drift at the city level, consistent with passive cultural processes leading to large-scale dialect differences. We did not find a strong signal for dialect or clinal differences between parks within cities, suggesting that birds did not actively converge on a group level signal, as expected under the group membership hypothesis. We demonstrate the robustness of our findings and offer an explanation that unifies the results of prior monk parakeet vocalization studies.

中文翻译：

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对和尚鹦鹉联络呼叫的多级贝叶斯分析显示欧洲城市之间的方言

发声的地理差异为动物文化提供了强有力的证据，其模式可能来自几代人的社会学习和传播。大多数关于鸟类声音变异进化的研究主要集中在雀形目鸟类的固定曲目、领地鸣叫上。因此，为了更全面地理解声音方言的演变，有必要对开放式学习者和发声具有其他功能的环境中的声音交流进行研究。鹦鹉是开放式的发声学习者，利用发声进行社会接触和协调。鹦鹉发声的地理变异通常采取不同的区域变异（称为方言）或基于地理距离的分级变异（称为临床变异）的形式。在这项研究中，我们记录了僧侣鹦鹉（Myiopsitta monachus）在欧洲入侵范围内多个空间尺度（即公园和城市）的情况。然后，我们使用多级贝叶斯模型和敏感性分析来比较呼叫，这种新颖的方法使我们能够在多个空间尺度上明确比较发声。我们发现对城市层面的创始人效应和/或文化漂移的支持，与导致大规模方言差异的被动文化过程一致。我们没有发现城市内公园之间的方言或临床差异的强烈信号，这表明鸟类并没有像群体成员假设所预期的那样积极地聚集在群体水平信号上。我们证明了我们研究结果的稳健性，并提供了统一先前僧侣鹦鹉发声研究结果的解释。