Data from: Causes and consequences of individual variation in the extent of post-juvenile moult in the blue tit Cyanistes caeruleus (Passeriformes: Paridae)

Moult, comprising the growth or replacement of feathers in birds, is an energetically demanding process. As a result, in many species, the extent of the post-juvenile moult can vary substantially. However, the reasons underlying this variation remain poorly understood, and the potential life-history consequences of variation in moult extent are even less clear. In the present study, we aimed to use individual-specific data to identify factors affecting the extent of the post-juvenile moult in a population of over 2500 blue tits Cyanistes caeruleus Linnaeus 1758, and to assess the consequences of individual variation in moult extent on reproduction in the first year of life. There was a substantial sex difference in post-juvenile moult extent, with males moulting more extensively than females. Putative immigrant birds had moulted on average less than those born locally. However, there was little evidence of carry-over effects of the natal environment on moult extent because we found no relationship between moult extent and fledging date or nestling mass. Evidence that moult extent, and hence feather brightness, affected subsequent reproductive success was limited. Moult extent had no effect on recruitment in males, although female recruits had moulted significantly less than nonbreeders. Because it was not influenced by features of the natal environment, moult extent may not be an honest signal of individual quality in C. caeruleus. As a result, the potential consequences of variation in moult extent for fitness are likely to be small.换羽（moult）指鸟类羽毛的生长与更替，是一项能量消耗极高的生理过程。因此，在多数鸟类物种中，幼后换羽（post-juvenile moult）的程度存在显著个体差异。然而，该差异的形成机制仍不甚明确，而换羽程度变异对物种生活史的潜在影响更是知之甚少。本研究依托包含超过2500只蓝山雀（Cyanistes caeruleus Linnaeus, 1758）的个体水平数据集，旨在明确影响其幼后换羽程度的关键因素，并评估换羽程度的个体差异对个体当年繁殖成功率的影响。 研究结果显示，幼后换羽程度存在显著性别差异：雄性蓝山雀的换羽程度显著高于雌性。疑似外来迁入个体的平均换羽程度显著低于本地出生个体。不过，本研究未发现换羽程度与出飞日期、雏鸟体重间存在关联，提示出生环境对换羽程度的遗留效应（carry-over effect）并不显著。关于换羽程度（进而影响羽毛亮度）对后续繁殖成功率的影响，相关证据较为有限。换羽程度对雄性的种群补充率无显著影响，但雌性补充个体的换羽程度显著低于未繁殖个体。由于换羽程度不受出生环境特征的调控，蓝山雀的换羽程度或许并非个体质量的诚实信号（honest signal）。综上，换羽程度的变异对个体适合度（fitness）的潜在影响可能较小。