Predicting the range of variation over which organisms can adjust to environmental change is a major challenge in ecology^1,2. This is exemplified in migratory birds which experience changes in different habitats throughout the annual cycle³. Earlier studies showed European population trends declining strongest in migrant species with least adjustment in spring arrival time^4,5. Thus, the increasing mismatches with other trophic levels in seasonal breeding areas^6,7 probably contribute to their large-scale decline. Here we quantify the potential range of adjusting spring arrival dates through modifying migration speeds by reviewing 49 tracking studies. Among-individual variation in migration speed was mainly determined by the relatively short stop-over duration. Assuming this population response reflects individual phenotypic plasticity, we calculated the potential for phenotypic plasticity to speed-up migration by reducing stop-over duration. Even a 50% reduction would lead to a mere two-day advance in arrival, considering adjustments on the final 2,000 km of the spring journey. Hence, in contrast to previous studies^8,9,10, flexibility in the major determinant of migration duration seems insufficient to adjust to ongoing climate change, and is unlikely to explain some of the observed arrival advancements in long-distance migrants.

预测生物可以适应环境变化的变化范围是生态学^1,2的一项重大挑战。以候鸟为例，候鸟在整个年度周期^3中经历了不同栖息地的变化。较早的研究表明，欧洲人口趋势在移徙物种中下降幅度最大，春季到达时间的调整幅度最小^4,5。因此，季节性繁殖区与其他营养水平的失配与日俱增^6,7可能是造成其大规模下降的原因。在这里，我们通过回顾49个跟踪研究，通过修改迁移速度来量化调整春季到达日期的潜在范围。个体间迁移速度的变化主要由相对较短的停留时间决定。假设这种种群反应反映了个体的表型可塑性，我们通过减少停留时间来计算表型可塑性加速迁移的潜力。考虑到对春季行程最后2,000公里的调整，即使减少50％，也只能提前两天到达。因此，与先前的研究^8,9,10相反移民持续时间的主要决定因素的灵活性似乎不足以适应不断变化的气候变化，并且不可能解释观察到的长途移民的某些到达进展。