The length of time songbirds remain at a migratory stopover site is likely regulated by a daily stay/go decision informed by fat stores and weather conditions, but the finer‐scale timing of this decision and associated pre‐departure behaviours are still poorly understood. Using automated radiotelemetry of free‐living songbirds captured at a migratory stopover site in spring, we tested whether individuals change their locomotor activity near sunset on their migratory departure day compared to their non‐departure days. To do so, we extracted precise transition times between diurnal activity and nocturnal inactivity, which always precedes departure, using changepoint analysis of radio transmission signal strength. Among four warbler species, individuals extended diurnal activity by 8–19 min towards sunset on their departure day. In three species, this extension was significant. In contrast, white‐throated sparrows significantly shortened diurnal activity on their departure day by 13 min, also towards sunset. This is the first study to detect and quantify a change in locomotor activity schedule on departure versus non‐departure days in free‐living songbirds, and is consistent with the hypothesis that birds engage in pre‐departure preparatory behaviours near sunset.

中文翻译：

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自由活动的鸣禽在出发前和出发日的中途停留运动时间有所不同

鸣禽停留在迁徙地点的时间长短可能受脂肪储存和天气状况告知的每日停留/离开决定的控制，但是对该决定的更精细时机和相关的出发前行为仍然知之甚少。使用春季在迁徙中途停留地点捕获的自由活动鸣禽的自动无线电遥测技术，我们测试了在迁徙出发日与非出发日相比，个体是否在日落附近改变了自发活动。为此，我们使用无线电传输信号强度的变化点分析提取了每日活动和夜间活动之间的精确转换时间，该转换时间始终在出发前。在四种莺鸟中，个体在出发日的日落时间延长了8-19分钟的昼夜活动。在三个物种中 这一扩展意义重大。相比之下，白喉麻雀在出发日的白天活动也大大缩短了13分钟，也接近日落。这是第一项检测和量化自由活动鸣鸟离港日与非离港日运动活动时间表变化的研究，并且与鸟类在日落附近从事离港前准备行为的假设相一致。