Recently, there has been an increased effort to unravel selective factors behind female song evolution in songbirds. Female birds which produce songs may sing either solo or in duets; although the 2 vocal performances likely evolved through different selection forces and mechanisms, the majority of large-scale studies to date have focused only on duetting or female song in general (pooling female solo song and duetting into a single category). Hence, here we estimate the effect of behavioral life-history traits (territoriality, social bonds, and cooperative breeding) and environmental productivity on the occurrence of female solo song and duetting separately in songbirds of South Africa and Lesotho. The focal region is characterized by subtropical/tropical climate, clear spatial environmental productivity gradient, and detailed knowledge on avian species distribution and behavioral life-history traits. Phylogenetically informed comparative analyses revealed that species where females produce only solo songs exhibited higher levels of territoriality than species with nonsinging females (in an univariable model) but, simultaneously, lower levels than duetting species. Although both species with female solo song and duetting establish mainly long-term social bonds, the former defend their territories seasonally while the latter exhibit mainly year-round territoriality. Cooperative breeding and environmental productivity were not associated with the distribution of female solo song and duetting in any model. Our results indicate that when exploring female song ecology and evolution, female solo song and duetting are likely to be distinct song categories associated with different levels of territoriality.

中文翻译：

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女性独唱和二重唱与鸣禽的不同地域性相关

最近，人们加大了努力来揭示鸣禽中女性歌曲进化背后的选择性因素。产歌的雌鸟可以独唱或二重唱。尽管这两种声乐表演可能是通过不同的选择力和机制演变而来的，但迄今为止，大多数大型研究都只集中在二重唱或女性歌曲上（将女性独唱和二重唱合为一类）。因此，在这里我们估计了行为生活史特征（地域性，社会纽带和合作繁殖）和环境生产力对南非和莱索托鸣禽中女性独唱和二重唱的影响。重点区域的特征是亚热带/热带气候，明显的空间环境生产力梯度，以及有关鸟类物种分布和行为生活史特征的详细知识。从系统发育学角度进行的比较分析表明，雌性仅产生独唱的物种的地域性水平高于雌性不唱歌的物种（在单变量模型中），但同时水平却比二重性物种低。尽管带有雌性独唱和二重唱的两个物种主要建立长期的社会纽带，但前者在季节上捍卫自己的领土，而后者则主要表现出全年的领土地位。在任何模型中，合作繁殖和环境生产力都与雌性独唱和二重唱的分布无关。我们的结果表明，在探索女性歌曲的生态和演变时，