Data from: Delayed dispersal and the costs and benefits of different routes to independent breeding in a cooperatively breeding bird

Why sexually mature individuals stay in groups as nonreproductive subordinates is central to the evolution of sociality and cooperative breeding. To understand such delayed dispersal, its costs and benefits need to be compared with those of permanently leaving to float through the population. However, comprehensive comparisons, especially regarding differences in future breeding opportunities, are rare. Moreover, extraterritorial prospecting by philopatric individuals has generally been ignored, even though the factors underlying this route to independent breeding may differ from those of strict philopatry or floating. We use a comprehensive predictive framework to explore how various costs, benefits and intrinsic, environmental and social factors explain philopatry, prospecting, and floating in Seychelles warblers (Acrocephalus sechellensis). Not only floaters more likely obtained an independent breeding position before the next season than strictly philopatric individuals, but also suffered higher mortality. Prospecting yielded similar benefits to floating but lower mortality costs, suggesting that it is overall more beneficial than floating and strict philopatry. While prospecting is probably individual-driven, although limited by resource availability, floating likely results from eviction by unrelated breeders. Such differences in proximate and ultimate factors underlying each route to independent breeding highlight the need for simultaneous consideration when studying the evolution of delayed dispersal.

性成熟个体以非繁殖从属者的身份留在群体中这一现象，是社会性演化与合作繁殖研究的核心议题。要理解这类延迟扩散（delayed dispersal）现象，需将其对应的成本与收益，与永久离开出生群体、在种群中漂泊的个体的成本与收益进行对比。然而，针对该现象的全面比较研究，尤其是涉及未来繁殖机会差异的相关研究仍较为匮乏。此外，具有留巢习性的个体所开展的领域外探查行为通常被忽视，尽管该独立繁殖路径背后的驱动因素，可能与严格留巢或漂泊繁殖路径存在差异。本研究依托全面的预测框架，探究各类成本、收益以及内在、环境与社会因素如何解释塞舌尔苇莺（Acrocephalus sechellensis）的留巢、领域外探查与漂泊行为。研究结果显示，相较于严格留巢个体，漂泊者不仅更有可能在下一个繁殖季前获得独立繁殖领地，同时其死亡风险也更高。领域外探查可获得与漂泊相近的收益，但死亡成本更低，这表明其整体上比漂泊与严格留巢更具适应性优势。尽管领域外探查可能受资源可获得性限制，但总体为个体自主发起的行为；而漂泊行为则大概率源于与繁殖者无亲缘关系的个体的驱逐。各独立繁殖路径背后的近因与远因存在上述差异，这凸显了在研究延迟扩散演化时，需同时兼顾各类因素的必要性。