Data: Direct and indirect effects of high temperatures on fledging in a cooperatively breeding bird

High temperatures and low rainfall consistently constrain reproduction in arid-zone bird species. Understanding the mechanisms underlying this pattern is critical for predicting how climate change will influence population persistence and to inform conservation and management. In this study, we analysed Southern Pied Babbler Turdoides bicolor nestling survival, daily growth rate and adult investment behaviour during the nestling period over three austral summer breeding seasons. High temperatures were associated with lower body mass, shorter tarsi, and reduced daily growth rates of nestlings. Our piecewise structural equation models suggested that direct impacts of temperature had the strongest influence on nestling size and daily growth rates for both 5-day-old and 11-day-old nestlings, followed by temperature-related adjustments to provisioning rates by adults. Rainfall and group size influenced the behaviour of provisioning adults but did not influence nestling growth or survival. Adjustments to adult provisioning strategies did not compensate for direct negative effects of high air temperatures on nestling size or daily growth rates. Detailed mechanistic data like these allow us to model the pathways by which high temperature causes nest failure. In turn, this could allow us to design targeted conservation action to effectively mitigate climate effects.

持续的高温与少雨环境始终制约着干旱区鸟类的繁殖活动。明晰该现象背后的作用机制，对于预测气候变化如何影响种群存续，并为物种保护与管理工作提供科学支撑至关重要。本研究针对三个南半球夏季繁殖季的斑鸫鹛（Southern Pied Babbler, Turdoides bicolor），分析了其雏鸟阶段的存活率、日生长速率以及成鸟的育雏投入行为。研究结果表明，高温与雏鸟较低的体质量、更短的跗跖长度以及更低的日生长速率显著相关。我们构建的分段结构方程模型（piecewise structural equation models）显示，无论是5日龄还是11日龄的雏鸟，温度的直接影响对其体型与日生长速率的作用最强，其次是成鸟依据温度变化调整的育雏投喂速率。降雨量与群体规模会影响成鸟的育雏行为，但并未对雏鸟的生长与存活产生显著影响。成鸟育雏策略的调整，未能抵消高温对雏鸟体型与日生长速率造成的直接负面影响。此类精细化的机制研究数据，能够帮助我们构建高温引发雏巢失败的作用路径模型，进而可据此设计针对性保护措施，有效减缓气候变化带来的负面影响。