Data from: Programmed and flexible: long-term Zugunruhe data highlight the many axes of variation in avian migratory behaviour

Studies of Zugunruhe—the “migratory restlessness” behaviour of captive birds—have been integral to our understanding of animal migration, revealing an inherited propensity to migrate and an endogenous timing and navigation system. However, differences between Zugunruhe in captivity and migration in the wild call for more data, in particular on variation within and among taxa with diverse migration strategies. Here, we characterise Zugunruhe in a long-term dataset of activity profiles from stonechats (genus Saxicola) with diverse migratory phenotypes (976 migration periods from 414 birds), using a flexible and consistent quantitative approach based on changepoint analysis. For East African, Austrian, Irish, and Siberian stonechats and hybrids, we report key inter-population differences in the occurrence, timing, and intensity of Zugunruhe. In line with expectations, we found the highest Zugunruhe intensity in the longest-distance migrants, more variable patterns in short-distance migrants, and intermediate characteristics of hybrids relative to their parental groups. Inter-population differences imply high evolutionary lability of Zugunruhe timing within a robustly structured annual cycle. However, counter to theory, Irish partial migrants showed no segregation between migrant and resident individuals, and previously reported nocturnal restlessness was confirmed for resident African stonechats. Further features of nocturnal restlessness that did not align with migratory behaviour of stonechats were juvenile nocturnal restlessness even prior to postjuvenile moult, and protandry in spring, although stonechats winter in heterosexual pairs. Importantly, Zugunruhe of all populations declined with age, and the intensity of an individual bird’s Zugunruhe was correlated with activity levels during other parts of the annual cycle. Our results confirm endogenous, population-specific migration programmes, but also reveal apparent discrepancies between Zugunruhe and migration in the wild. We thus highlight both the continued potential of Zugunruhe study and the need for circumspect interpretation when using migratory restlessness to make inferences about migration in the wild.

对Zugunruhe（迁徙躁动）——圈养鸟类的“迁徙躁动”行为——的研究是我们理解动物迁徙的核心工作，其揭示了鸟类与生俱来的迁徙倾向，以及内源性的时间调控与导航系统。然而，圈养环境下的迁徙躁动与野生鸟类的迁徙行为之间存在差异，这亟需更多研究数据，尤其是针对具备不同迁徙策略的分类群内部及分类群间的变异情况。

本研究基于变点分析（changepoint analysis）构建了一套灵活且统一的定量分析方法，对具备不同迁徙表型的石鵖属（Saxicola）鸟类的长期活动数据集进行了特征刻画，该数据集涵盖414只个体的976个迁徙周期。针对东非、奥地利、爱尔兰、西伯利亚的石鵖及其杂交个体，我们报道了迁徙躁动在发生概率、发生时间与强度上的关键种群间差异。

与预期相符，我们在迁徙距离最远的类群中观测到了最高的迁徙躁动强度，短距离迁徙类群的躁动模式则更为多变，而杂交个体的迁徙躁动特征介于其亲本类群之间。种群间的差异表明，在结构稳定的年度周期内，迁徙躁动的时间调控具有较高的进化可塑性。然而，与理论预期相悖的是，爱尔兰的部分迁徙类群并未表现出迁徙个体与居留个体间的行为分化，且我们证实了此前报道的居留型非洲石鵖存在夜间躁动行为。

此外，还有两项与石鵖迁徙行为不符的夜间躁动特征：一是稚鸟在完成稚后换羽（postjuvenile moult）前就已表现出夜间躁动，二是春季存在雄性先熟（protandry）现象——尽管石鵖是以异性配对的方式越冬。值得注意的是，所有种群的迁徙躁动强度均随年龄增长而减弱，且个体的迁徙躁动强度与其年度周期内其他时段的活动水平呈显著相关。

我们的研究结果证实了迁徙躁动具有内源性的种群特异性迁徙程序，但同时也揭示了圈养环境下的迁徙躁动与野生鸟类的迁徙行为之间存在明显差异。因此，本研究既凸显了迁徙躁动研究的持续价值，也提醒研究者在利用迁徙躁动行为推断野生鸟类迁徙情况时，需保持审慎的解读态度。