尾羽在鸟类的繁殖中起重要作用。多数鸟类会在繁殖期换上更长更艳的尾羽，而山鹪莺属一些种类却换上更短的尾羽，我们称之为逆变化尾羽。在全球 9000 多种鸟类中，已知有这种尾羽的仅十多种。至今对此现象机理的研究仍是空白。. 本团队根据多年研究积累，提出山鹪莺逆变化尾羽的进化机制假说：山鹪莺为满足繁殖育幼的需要，在繁殖期和非繁殖期对性选择和自然选择作出了不同的权衡，导致了逆变化尾羽的出现。为验证该假说，我们以黄腹山鹪莺（Prinia flaviventris）为模式种，采用室内控制实验、野外观测实验和模型模拟等手段，对三个关键问题进行验证，即非繁殖期性选择作用的存在性、交配后更换短尾羽的迫切性以及繁殖期短尾羽存在的必要性，检测生活史不同阶段性选择和自然选择作用的差异，从而揭示尾羽逆变化现象的进化机制及其对应的生存对策，为物种进化的认识与理论发展提供新知识。

Tails are vital for Aves to survive and reproduce. Most birds will moult longer or more beautiful tails in breeding season. Inversely, some pecies in Prinia will moult shorter tails, which we call inverse-changed tails.Among more than 9000 avian species in the world, only above ten species own these tails. Until now,this phenomenon is still under a mystery..Basing on the clues of our researches, we propose a hypothesis on the evolutional mechnism of the inverse-changed tail, in which different trade-offs between sexual selection and natural selection occur in different stages of annual life history, respectively. To test the importance of sexual selection and natural selection in different stages, we apply multiply metholds with control tests,ourdoor experiments.and model stimulation and design three types of experiments with Prinia flaviventris: the existence of sexual selection in non-breeding season, the urgency of tail moulting after copulation and the necessity of shorter tail in breeding season. Hence, we will uncover the evolutional mechanism and survival strategies of the species with inverse-changed tailes and replenish new knowledge and contents on.species evolution and survival strategies.