Data from: Pairing context determines condition-dependence of song rate in a monogamous passerine bird

Condition-dependence of male ornaments is thought to provide honest signals on which females can base their sexual choice for genetic quality. Recent studies show that condition-dependence patterns can vary within populations. Although long-term association is thought to promote honest signalling, no study has explored the influence of pairing context on the condition-dependence of male ornaments. In this study, we assessed the influence of natural variation in body condition on song rate in zebra finches (Taeniopygia guttata) in three different situations: during short and long encounters with an unfamiliar female, and within heterosexual mated pairs. We found consistent individual differences in male directed and undirected song rate. Moreover, body condition had a positive effect on song rate in paired males. However, male song rate was not influenced by body condition during short or long encounters with unfamiliar females. Song rate appears to be an unreliable signal of condition to prospective females as even poor-condition birds can cheat and sing at a high rate. By contrast, paired females can reliably use song rate to assess their mate's body condition, and possibly the genetic quality. We propose that species' characteristics, such as mating system, should be systematically taken into account to generate relevant hypotheses about the evolution of condition-dependent male ornaments.

雄性装饰性状的条件依赖性被认为是一类诚实信号，雌性可依托此类信号，基于雄性的遗传质量开展性选择。近期研究表明，种群内部的条件依赖性模式存在差异。尽管学界认为长期配偶关系可促进诚实信号传递，但目前尚无研究探讨配对情境对雄性装饰性状条件依赖性的影响。本研究以斑胸草雀（Taeniopygia guttata）为研究对象，在三种不同情境下评估了身体状况的自然变异对其鸣唱率的影响：与陌生雌性进行短期、长期接触时，以及处于异性配对关系的个体间。研究发现，雄性的定向鸣唱率与非定向鸣唱率均存在稳定的个体差异。此外，身体状况对配对雄性的鸣唱率具有显著正向影响。但在与陌生雌性进行短期或长期接触时，雄性的鸣唱率并不受身体状况的影响。对于潜在配偶雌性而言，鸣唱率并非可靠的身体状况信号，因为即便身体状况较差的个体也能通过欺骗手段维持高鸣唱率。与之相反，已配对的雌性可通过鸣唱率可靠地评估配偶的身体状况，乃至其遗传质量。本研究提出，应系统考量物种的交配系统等特征，以构建关于条件依赖性雄性装饰性状演化的合理假说。