Data from: Wintering areas predict age-related breeding phenology in a migratory passerine bird

Understanding connections between breeding, stopover and wintering grounds for long-distance migratory birds can provide important insight into factors influencing demography and the strength of carry-over effects among various periods of the annual cycle. Using previously described, multi-isotope (δ13C, δ15N, δ2H) feather isoscapes for Africa, we identified the most probable wintering areas for house martins (Delichon urbica) breeding at Badajoz in southwestern Spain. We identified two most-probable wintering areas differing in latitude in West Africa. We found that the probability to winter in the northern region was related to age and sex of individuals. Specifically, experienced males (i.e., two years or older) winter in the northern area with a greater probability than experienced females, whereas first-year females winter in the northern area with a greater probability than first-year males. In addition, wintering area was correlated with breeding phenology, with individuals wintering in the northern area initiating their clutches earlier than those wintering in the southern area. For birds wintering in the northern area, there was no relationship between age and clutch initiation date. In contrast, young birds wintering in the southern area initiated their clutches earlier than experienced birds wintering in this area. There was no significant correlation between wintering area and clutch size or the number of fledglings produced. We hypothesize that the relationship among social status, population density and winter habitat quality should be the most important driver of the carry-over effect we found for this population

解析长途迁徙鸟类繁殖地、停歇地与越冬地之间的关联，可为阐明影响种群统计学特征的各类因素以及年度周期不同阶段间携带效应（carry-over effects）的强度提供关键见解。本研究依托此前已发表的非洲区域多同位素（multi-isotope，δ13C、δ15N、δ2H）羽毛同位素等值图（feather isoscapes），对西班牙西南部巴达霍斯地区繁殖的白腹毛脚燕（Delichon urbica）的高概率越冬区域进行了确定。研究共识别出西非地区两处纬度存在差异的高概率越冬区域。研究发现，个体在北部区域越冬的概率与其年龄和性别相关：具体而言，成体雄鸟（2龄及以上个体）相较于成体雌鸟，更倾向于在北部区域越冬；而当年幼雌鸟则比当年幼雄鸟更大概率选择北部区域越冬。此外，越冬区域与繁殖物候存在显著关联，在北部区域越冬的个体，其产卵起始时间早于在南部区域越冬的个体。对于在北部区域越冬的个体而言，年龄与产卵起始日期并无显著相关性；与之相反，在南部区域越冬的幼鸟，其产卵起始时间早于该区域内的成体个体。越冬区域与窝卵数或出飞幼鸟数量之间未呈现显著相关性。本研究提出假说：个体社会地位、种群密度与越冬生境质量之间的关联，应为本次研究中观测到的该种群携带效应的核心驱动因素。