Data and code from Departure, routing and landing decisions of long-distance migratory songbirds in relation to weather

Migrating birds flexibly adjust their individual migratory decisions, i.e. departing, routing and landing, based on intrinsic (e.g. energy stores) and extrinsic (e.g. landscape features and weather) factors modulating the endogenous stimuli. So far, these decisions have mostly been studied separately. Notably, we lack information on which factors landing decisions during active flight are based on. Therefore, we simultaneously recorded all three decisions in free-flying long-distance migratory songbirds in a coastal stopover area via regional-scale radio-telemetry and related them to the prevailing weather. Birds departed under favourable weather conditions resulting in specific nights with increased departure probability. Once departed, birds could either fly offshore or take a route along the coast, which was predicted by wind support. Radio-tracking revealed that departed individuals more likely interrupted their migratory endurance flight under overcast or headwind conditions. Studying departure, routing and landing decisions in concert, we highlight the importance of weather as a common driver across all migratory decisions. By radio-tracking individuals between stopovers, we provide evidence that avoidance of adverse weather conditions is an important function of stopover. Understanding how birds adjust migratory decisions and how they affect the timing of migration and survival is key to link migration performance to individual fitness.

迁徙鸟类会基于内在（如能量储备）与外在（如景观特征、天气）等调控内源刺激的因素，灵活调整个体的三类迁徙决策——即启程、航线选择与着陆行为。迄今为止，学界对上述三类迁徙决策的研究大多相互独立。值得注意的是，目前仍缺乏关于鸟类在主动飞行过程中着陆决策依据何种因素的相关数据。为此，本研究通过区域尺度无线电遥测技术（radio-telemetry），在沿海停歇地（stopover area）对自由飞行的长距离迁徙鸣禽的三类迁徙决策进行同步记录，并将其与实时天气状况相关联。研究发现，鸟类会选择在适宜的天气条件下启程迁徙，由此形成了一批启程概率显著升高的特定夜间时段。启程后，鸟类可选择飞越近海或沿海岸飞行，该航线选择行为可通过风力助力情况进行预测。无线电追踪结果显示，已启程的个体在遭遇阴天或逆风天气时，更易中断其迁徙续航飞行（migratory endurance flight）。本研究通过同步整合三类迁徙决策的分析，明确了天气作为贯穿所有迁徙决策的共同驱动因素的关键作用。通过对两次停歇间隔的个体开展无线电追踪，本研究证实：规避不利天气条件是鸟类停歇行为的一项重要生态功能。阐明鸟类如何调整迁徙决策，以及这些决策如何影响迁徙时间安排与存活状况，是将迁徙表现与个体适合度（individual fitness）建立关联的核心所在。