The duets of birds have intrigued biologists for a long time, yet much remains unknown about the evolution of these striking collective displays. This is partly because previous studies on duet evolution have been biased to songbirds and neglected other bird groups. In songbirds, the absence of migration has been found to predict the occurrence of duetting, indirectlysupporting the idea that duet communication is linked with pair bonding. Here, we used phylogenetic comparative analyses in a sedentary clade of non-songbirds, the barbets (Capitonidae), to reveal new correlates of duet evolution. We found (i) that duets evolved several times independently in different barbet lineages and (ii) that duetting evolved in association with group living (i.e. the presence of helpers or non-breeding adults during the breeding period), but not with sexual monochromatism or habitat type. Our findings are consistent with a duet function in mate guarding and dominance against subordinate group members as well as joint territory defence. Altogether, the results highlight the importance of the social environment for the evolution of collective signalling.

长期以来，鸟类的二重唱一直吸引着生物学家，但关于这些引人注目的集体表演的进化，仍有许多未知之处。这部分是因为之前关于二重奏进化的研究偏向于鸣禽，而忽视了其他鸟类群体。在鸣禽中，已发现没有迁徙可以预测二重唱的发生，间接支持二重唱交流与配对联系有关的观点。在这里，我们在非鸣禽的久坐进化枝中使用系统发育比较分析，barbets (Capitonidae)，以揭示二重奏进化的新关联。我们发现 (i) 二重奏在不同的 barbet 谱系中独立进化了几次，以及 (ii) 二重奏的进化与群体生活有关（即在繁殖期间出现助手或非繁殖成年人），但与性单色性或栖息地类型无关。我们的研究结果与在配偶保护和支配下属群体成员以及联合领土防御方面的二重奏功能是一致的。总之，结果强调了社会环境对集体信号进化的重要性。