Passerine moult shows two well‐known although intriguing characteristics: 1) a varying subset of wing feathers are retained during certain moult episodes, and 2) the identity of the replaced feathers is not random. However, the rules that underlie these moult features are largely unknown. Non‐randomness could arise under time and energy constraints if feathers differed in their importance, such that they could be ordered following a hypothetical moult rank. This rule predicts a nested relationship among wing‐feather moult phenotypes, where phenotypes of smaller extent would consist of subsets of the wing feathers replaced in phenotypes of larger extent. Here, we analysed a dataset of 3909 preformative and prealternate moult phenotypes from 434 Holarctic and Neotropical passerine species. We found that passerine wing‐feather moult was nested (nodf = 84.31). However, systematic imperfections in the nestedness pattern led us to test whether the existence of different feather moult ranks may increase nestedness in homogeneous subsets of moult phenotypes. We tested this hypothesis between moult episodes and found that nestedness increased for the preformative moult (nodf = 90.99) and decreased for the prealternate moult (nodf = 67.28). We further analysed the adaptive meaning of different moult ranks associated with feather mass, feather exposure and feather contribution to flight. Overall, these three feather traits explained 53.74% of the variation in the priority of wing‐feather replacement, with exposure having a stronger explanatory power than the other two traits. Our findings provide a first model to interpret variation of wing‐feather moult phenotypes in passerines, and outlines the relevance of season for passerine moult, suggesting a dynamic link between moult expression and plumage requirements.

中文翻译：

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蜕皮的嵌套及其不完善之处：揭示雀形翅羽蜕皮规则本质的见解

雀形目蜕皮显示出两个众所周知但有趣的特征：1）在某些蜕皮事件中保留了不同种类的翼羽，以及2）被替换的羽毛的身份不是随机的。但是，这些多态特征的基础规则尚不清楚。如果羽毛的重要性不同，则在时间和精力的限制下可能会出现非随机性，从而使它们可以按照假定的换羽等级排序。该规则预测了翅羽蜕变表型之间的嵌套关系，其中较小范围的表型将由替换为较大范围的表型的机翼羽毛的子集组成。在这里，我们分析了来自434种Holarctic和Neotropical雀形目物种的3909个转化性和替代性蜕变表型的数据集。我们发现雀形翅羽蜕皮被嵌套（nodf = 84.31）。但是，嵌套模式中的系统缺陷使我们测试了不同的羽毛换羽等级是否会增加换羽表型的同质子集中的嵌套性。我们在换羽事件之间检验了这一假设，发现对于形成性换羽（nodf = 90.99）嵌套度增加，而对于另类换羽（nodf = 67.28），嵌套度降低。我们进一步分析了与羽毛质量，羽毛暴露和羽毛对飞行的贡献相关的不同蜕皮等级的适应性含义。总体而言，这三个羽毛特征解释了机翼羽毛替换优先级变化的53.74％，而暴露比其他两个特征具有更强的解释力。