Data from: Individual consistency of long-distance migration in a songbird: significant repeatability of autumn route, stopovers and wintering sites but not in timing of migration

Through new tracking techniques, data on timing and routes of migration in long-distance migrant birds are accumulating. However, studies of the consistency of migration of the same individuals between years are still rare in small-sized passerine birds. This type of information is important to understand decisions and migration abilities at the individual level, but also for life history theory, for understanding carry over effects between different annual cycle stages and for conservation. We analysed individual repeatability of migration between years in great reed warblers Acrocephalus arundinaceus; a medium-sized European songbird migrating to sub-Saharan Africa. In seven males, with geolocator data from 2–4 yr per bird, we found low to moderate (non significant) repeatability in timing of migration parameters (R ≤ 0.41), but high (and significant) repeatability for most spatial parameters, i.e. autumn route (R = 0.64) and stopover sites (R = 0.59–0.87) in Europe, and wintering sites (R = 0.77–0.99) in sub-Saharan Africa. This pattern of high spatial but low temporal within-individual repeatability of migration between years contrasts other tracking studies of migrating birds that generally have found consistency in timing but flexibility in routes. High spatial consistency of migration in the great reed warbler may be due to it being a specialist in wetlands, an unevenly distributed habitat, favouring a strategy of recurrence at previously visited sites. Low temporal repeatability may be caused by large between-year variation in carry-over effects from the breeding season, high flexibility in decision rules during migration or high sensitivity to environmental factors (weather, wind) during migration.借助新型追踪技术，有关长途迁徙鸟类的迁徙时序与迁徙路径的数据正持续累积。然而，针对同一只个体跨年度迁徙一致性的研究，在小型雀形目鸟类中仍较为匮乏。这类信息不仅有助于理解个体层面的迁徙决策与迁徙能力，也可为阐释生活史理论、解析年度周期不同阶段间的携带效应，以及开展物种保护工作提供关键支撑。本研究针对迁徙至撒哈拉以南非洲的欧洲中型鸣禽——大苇莺（great reed warbler，*Acrocephalus arundinaceus*），分析了其跨年度迁徙的个体重复性。我们共获取了7只雄性个体的地理定位器（geolocator）数据，每只个体覆盖2至4个年度。分析结果显示：迁徙时序参数的个体重复性处于低至中等水平（无统计学显著性，R≤0.41）；而多数空间参数则表现出较高且显著的重复性，具体包括欧洲境内的秋季迁徙路径（R=0.64）与中途停歇地（R=0.59~0.87），以及撒哈拉以南非洲的越冬地（R=0.77~0.99）。这种“跨年度迁徙中空间参数重复性高、时序参数重复性低”的个体内模式，与此前多数鸟类迁徙追踪研究的结论形成鲜明反差——过往研究通常报道迁徙时序具有较高一致性，而迁徙路径则存在显著灵活性。大苇莺迁徙的空间一致性较高，可能与其湿地特化的生态位有关：湿地生境分布不均，因此这类鸟类更倾向于复用此前造访过的栖息位点。而迁徙时序的低重复性，则可能由以下因素导致：繁殖季携带效应在年度间存在显著差异、迁徙过程中的决策规则具有高度灵活性，或是迁徙期间对天气、风力等环境因素的敏感性较高。