Data from: African departure rather than migration speed determines variation in spring arrival in pied flycatchers

1. Properly timed spring migration enhances reproduction and survival. Climate change requires organisms to respond to changes such as advanced spring phenology. Pied flycatchers Ficedula hypoleuca have become a model species to study such phenological adaptations of long-distance migratory songbirds to climate change, but data on individuals’ time schedules outside the breeding season are still lacking.
2. Using light-level geolocators we studied variation in migration schedules across the year in a pied flycatcher population in the Netherlands, which sheds light on the ability for individual adjustments in spring arrival timing to track environmental changes at their breeding grounds.
3. We show that variation in arrival dates to breeding sites in 2014 was caused by variation in departure date from Sub-Saharan Africa, and not by environmental conditions encountered en route. Spring migration duration was short for all individuals, on average two weeks. Males migrated ahead of females in spring, while migration schedules in autumn were flexibly adjusted according to breeding duties. Individuals were therefore not consistently early or late throughout the year.
4. In fast migrants like the Dutch pied flycatchers, advancement of arrival to climate change likely requires changes in spring departure dates. Adaptation for earlier arrival may be slowed down by harsh circumstances in winter, or years with high costs associated with early migration.

1. 适时开展春季迁徙可提升繁殖成功率与个体存活率。气候变化迫使生物应对春季物候提前等环境变动，斑姬鹟（Pied flycatcher，Ficedula hypoleuca）已成为研究长距离迁徙鸣禽应对气候变化的物候适应性的经典模式物种，但目前仍缺乏繁殖季外个体迁徙时间安排的相关数据。
2. 本研究借助光强地理定位器（light-level geolocators），对荷兰境内的斑姬鹟种群全年的迁徙节律变化进行了分析，借此阐明个体可通过调整春季抵达繁殖地的时间，追踪繁殖地环境变化的能力。
3. 研究结果显示，2014年斑姬鹟抵达繁殖地的时间差异，源于其从撒哈拉以南非洲出发的时间差异，而非迁徙途中遭遇的环境条件。所有个体的春季迁徙时长均较短，平均仅为两周。春季迁徙中雄性早于雌性启程，而秋季迁徙节律则会根据繁殖任务灵活调整。因此，个体在全年的迁徙节奏并非始终保持早到或晚到的固定模式。
4. 对于荷兰斑姬鹟这类快速迁徙物种而言，为应对气候变化而提前抵达繁殖地，可能需要调整春季的出发时间。但冬季的恶劣环境，或是早期迁徙成本高昂的年份，可能会延缓其实现提前抵达的适应性进程。