Data from: Fitness, behavioral, and energetic trade-offs of different migratory strategies in a partially migratory species

Alternative migratory strategies can coexist within animal populations and species. Anthropogenic impacts can shift the fitness balance between these strategies leading to changes in migratory behaviors. Yet some of the mechanisms that drive such changes remain poorly understood. Here we investigate the phenotypic differences, and the energetic, behavioral, and fitness trade-offs associated with four different movement strategies (long- and short-distance migration, and regional and local residency) in a population of white storks (Ciconia ciconia) that has shifted its migratory behavior over the last decades, from fully long-distance migration towards year-round residency. To do this, we tracked 75 adult storks fitted with GPS/GSM loggers with triaxial acceleration sensors over 5 years, and estimated individual displacement, behavior, and overall dynamic body acceleration, a proxy for activity-related energy expenditure. Additionally, we monitored nesting colonies to assess individual survival and breeding success. We found that long-distance migrants travelled thousands of kilometers more throughout the year, spent more energy, and >10% less time resting compared to short-distance migrants and residents. Long-distance migrants also spent on average more energy per unit of time while foraging, and less energy per unit of time while soaring. Migratory individuals also occupied their nests later than resident ones, later occupation led to later laying date and reduced number of fledglings. However, we did not find significant differences in survival probability. Finally, we found phenotypic differences in the migratory probability, as smaller-sized individuals were more likely to migrate, and they might be incurring in higher energetic and fitness costs than larger ones. Our results shed light into the shifting migratory strategies in a partially migratory population and highlight the nuances of anthropogenic impacts on species behavior, fitness, and evolutionary dynamics.

动物种群与物种内部可共存多种迁徙策略。人为活动可改变这些策略间的适合度平衡，进而引发迁徙行为的改变。然而，驱动此类改变的部分机制仍未得到充分阐释。本研究针对近数十年间从完全长距离迁徙转向全年居留的白鹳（Ciconia ciconia）种群，探究其四种不同移动策略（长距离迁徙、短距离迁徙、区域居留与本地居留）相关的表型差异，以及能量、行为与适合度权衡关系。为此，我们对75只佩戴搭载三轴加速度传感器的GPS/GSM追踪器的成年白鹳开展了为期5年的追踪，估算个体移动距离、行为以及整体动态身体加速度——该指标可作为活动相关能量消耗的替代变量。此外，我们对筑巢种群进行监测，以评估个体存活率与繁殖成功率。研究结果显示，与短距离迁徙个体及居留个体相比，长距离迁徙个体全年多飞行数千公里，能量消耗更高，且休息时间减少超过10%。长距离迁徙个体在觅食时段的单位时间能量消耗也更高，而在翱翔时段的单位时间能量消耗则更低。迁徙个体的筑巢时间也晚于居留个体，筑巢延迟会导致产卵日期延后，且雏鸟出飞数量减少。但我们未发现存活率存在显著差异。最后，我们发现个体迁徙概率存在表型差异：体型更小的个体更倾向于迁徙，且相较于体型更大的个体，它们可能承担更高的能量与适合度成本。本研究结果阐明了部分迁徙种群的迁徙策略转变机制，并揭示了人为活动对物种行为、适合度及进化动态的影响细节。