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.对于迁徙动物而言，其年度周期中不同时段与地点所遭遇的环境条件，可能会对繁殖成功率产生影响。然而迄今为止，绝大多数研究仅考察了年度周期中特定阶段的影响，尽管厘清不同阶段间的交互作用机制，以及这些阶段与个体内在质量如何共同调节繁殖成功率，具有重要的研究价值。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 modelling）方法，探究了繁殖成功率的三类驱动因子：迁徙周期、个体质量与繁殖环境条件。我们构建的因果模型能够解释75%的繁殖成功率变异。研究结果显示，迁徙节律对繁殖成功率的影响可忽略不计，而前一次繁殖事件对当前繁殖成功率具有显著的正向影响。我们提出，即便对于长距离迁徙鸟类而言，个体质量与前一次、当前繁殖季的环境条件之间的交互作用，或许也是比迁徙节律更为关键的繁殖成功率驱动因子。本研究证实，结构方程模型是探究因果关系的极具潜力的研究工具。针对戴胜的应用结果表明，当前繁殖成功率与前一次繁殖成功率存在紧密关联。后续可开展整合迁徙与繁殖季天气、气候条件的补充分析，从而更全面深入地解析戴胜的年度周期，并进一步揭示繁殖成功率中携带效应（carry-over effects）的存在机制。