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，可为揭示影响种群动态以及年度周期各阶段间携带效应（carry-over effects）强度的相关因素提供重要学术见解。本研究依托已发表的非洲羽毛多同位素（δ¹³C、δ¹⁵N、δ²H）同位素地理分布图（isoscape），对西班牙西南部巴达霍斯地区繁殖的家燕（Delichon urbica）的最可能越冬地进行了识别。研究共识别出西非地区两个纬度分布存在差异的最可能越冬区域。结果显示，家燕选择北部越冬区的概率与其年龄和性别显著相关。具体而言，成体雄鸟（即两岁及以上个体）相较于成体雌鸟，更倾向于选择北部越冬区；而当年幼的雌鸟则较当年幼的雄鸟更大概率选择北部越冬区。此外，越冬区域与繁殖物候存在关联：选择北部越冬区的个体，其产卵启动时间早于选择南部越冬区的个体。对于选择北部越冬区的个体而言，其年龄与产卵启动日期并无显著关联。与之形成对比的是，选择南部越冬区的当年幼鸟，其产卵启动时间早于该区域内的成体个体。越冬区域与窝卵数以及出飞幼鸟数量均无显著相关性。我们提出假说：种群社会地位、种群密度与越冬栖息地质量之间的相互关系，是本研究观测到的该种群携带效应的核心驱动因素。