Precise timing of migration is crucial for animals targeting seasonal resources at locations encountered across their annual cycle. Upon departure, long-distance migrants need to anticipate unknown environmental conditions at their arrival site, and they do so with their internal annual clock. Here, we tested the hypothesis that long-distance migrants synchronize their circannual clock according to the phenology of their environment during the breeding season and therefore adjust their spring departure date according to the conditions encountered at their breeding site the year before. To this end, we used tracking data of Eurasian curlews from different locations and combined movement data with satellite-extracted green-up dates at their breeding site. The spring departure date was better explained by green-up date of the previous year, while arrival date at the breeding site was better explained by latitude and longitude of the breeding site, suggesting that other factors impacted migration timing en route. On a broader temporal scale, our results suggest that long-distance migrants may be able to adjust their migration timing to advancing spring dates in the context of climate change.

准确的迁徙时间对于动物在其年度周期中遇到的地点以季节性资源为目标至关重要。离开时，长途移民需要预测到达地点未知的环境条件，他们使用内部的年度时钟来做到这一点。在这里，我们检验了远距离迁徙者在繁殖季节根据其环境物候同步其生物钟的假设，因此根据前一年繁殖地点遇到的条件调整其春季出发日期。为此，我们使用了来自不同地点的欧亚鹬的跟踪数据，并将运动数据与卫星提取的繁殖地点的绿色日期相结合。春季出发日期最好用上一年的绿化日期来解释，途中。在更广泛的时间范围内，我们的结果表明，在气候变化的背景下，长途移民可能能够调整他们的迁移时间以提前春季日期。