Unravelling the processes between phenotypic plasticity and population dynamics in migratory birds.

Populations can rapidly respond to environmental change via adaptive phenotypic plasticity, which can also modify interactions between individuals and their environment, affecting population dynamics. Bird migration is a highly plastic resource-tracking tactic in seasonal environments. However, the link between the population dynamics of migratory birds and migration tactic plasticity is not well-understood. The quality of staging habitats affects individuals' migration timing and energy budgets in the course of migration and can consequently affect individuals' breeding and overwintering performance, and impact population dynamics. Given staging habitats being lost in many parts of the world, our goal is to investigate responses of individual migration tactics and population dynamics in the face of loss of staging habitat and to identify the key processes connecting them. We started by constructing and analysing a general full-annual-cycle individual-based model with a stylized migratory population to generate hypotheses on how changes in the size of staging habitat might drive changes in individual stopover duration and population dynamics. Next, through the interrogation of survey data, we tested these hypotheses by analysing population trends and stopover duration of migratory waterbirds experiencing the loss of staging habitat. Our modelling exercise led to us posing the following hypotheses: the loss of staging habitat generates plasticity in migration tactics, with individuals remaining on the staging habitat for longer to obtain food due to a reduction in per capita food availability. The subsequent increasing population density on the staging habitat has knock-on effects on population dynamics in the breeding and overwintering stage. Our empirical results were consistent with the modelling predictions. Our results demonstrate how environmental change that impacts one energetically costly life-history stage in migratory birds can have population dynamic impacts across the entire annual cycle via phenotypic plasticity. 种群因具备适应性的表型可塑性可以迅速响应环境变化，同时，表型可塑性也能够通过改变个体与其环境之间的相互作用而影响种群动态。迁徙是鸟类在季节性变化的环境中演化出的一种资源追踪型策略，其可塑性非常强。然而有关迁徙策略可塑性与候鸟种群动态之间的反馈过程尚不清楚。 迁徙中停地的质量影响着候鸟个体在迁徙过程中时间与能量的权衡，进而通过影响个体在繁殖和越冬阶段的表现来影响种群动态。由于世界范围内很多迁徙鸟类的中停地都在急剧减少，因此本文希望探究在迁徙中停地丧失的情况下，鸟类的迁徙策略与种群动态之间存在何种联结。 首先，我们构建了一个包含程式化迁徙种群全年周期的基于个体的模型，利用该模型提出了关于迁徙中停地的变化如何驱动候鸟个体停留时间和种群动态发生改变的假设，并通过对中国渤海湾地区迁徙中停的水鸟的调查数据的分析进行了验证。 我们的假设是：迁徙中停地的丧失会导致鸟类迁徙策略的改变，由于候鸟个体在中停地可获得的食物资源减少，它们会延长在中停地的停留时间以补充能量，由此引发中停地鸟类种群密度的增长，从而对整个生活史周期内候鸟繁殖和越冬阶段的种群动态产生了连锁反应。我们的实证研究结果与建模预测一致。 本研究表明，环境变化对迁徙候鸟生活史中某一个阶段的作用会通过表型可塑性对其整个周期的种群动态产生巨大影响。.

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© 2022 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.