Data from: Identifying drivers of breeding success in a long-distance migrant using structural equation modelling

In migrant animals, conditions encountered at various times and places throughout their annual cycle may affect breeding success. Yet, most studies so far have only investigated the effect of specific parts of the annual cycle, despite the importance to understand how different stages can interact and how these stages compare to intrinsic quality to properly modulate breeding success. Using a structural equation modelling approach, we investigated drivers of breeding success (migration cycle, individual quality, breeding conditions) in hoopoes (Upupa epops), a long-distant migrant. Our causal framework explained 75% of the variation in breeding success. The effect of the migration schedule was negligible, whereas the previous breeding attempt strongly influenced current breeding success. We suggest that the interplay of individual quality and environmental conditions during both previous and current breeding season may be more important drivers of breeding success than migration schedules, even in a long-distance migrant. We conclude that structural equation modeling is a promising tool to investigate causal relationships. Applied to hoopoes, we demonstrated that current breeding success is strongly linked to previous breeding success. Complementary analysis integrating weather and climate conditions during migration and the breeding season may provide a deeper and wider overview of the annual cycle of hoopoes and additional insights into the existence of carry-over effects in breeding success.

在迁徙动物中，其全年周期内不同时间与地点所遭遇的环境条件，可能会影响繁殖成功率。然而迄今为止，多数研究仅针对全年周期的特定阶段展开了影响效应探究，尽管明晰不同阶段间的交互作用，以及这些阶段如何与个体内在素质协同调节繁殖成功率，具有重要意义。本研究以长距离迁徙鸟类戴胜（Upupa epops）为研究对象，采用结构方程模型（Structural Equation Modeling）方法，探究了繁殖成功率的影响因子：迁徙周期、个体素质与繁殖环境条件。我们构建的因果模型框架可解释75%的繁殖成功率变异。迁徙节律对繁殖成功率的影响可忽略不计，而上一次繁殖行为则对当前繁殖成功率产生了显著影响。本研究认为，即便在长距离迁徙鸟类中，个体素质与前后繁殖季环境条件的交互作用，或许是比迁徙节律更为关键的繁殖成功率影响因子。综上，结构方程模型是探究因果关系的极具应用前景的工具。将该模型应用于戴胜种群后，本研究证实当前繁殖成功率与上一次繁殖成功率存在显著关联。后续可开展整合迁徙与繁殖季天气及气候条件的补充分析，以更全面深入地解析戴胜的全年生活周期，并进一步揭示繁殖成功率中携带效应（Carry-over Effects）的存在机制。