Data from: Novel energy-saving strategies to multiple stressors in birds: the ultradian regulation of body temperature

The present study aimed to examine thermoregulatory responses in birds facing two commonly experienced stressors, cold and fasting. Logging devices allowing long-term and precise access to internal body temperature were placed within the gizzards of ducklings acclimated to cold (5°C) or thermoneutrality (25°C). The animals were then examined under three equal four-day periods: ad libitum feeding, fasting, and re-feeding. Through the analysis of daily as well as short-term, or ultradian, variations of body temperature, we showed that while ducklings at thermoneutrality show only a modest decline in daily thermoregulatory parameters when fasted, they exhibit reduced surface temperatures from key sites of vascular heat exchange during fasting. The cold acclimated birds, on the other hand, significantly reduced their short-term variations of body temperature while increasing long-term variability when fasting. This phenomenon would allow the cold acclimated birds to reduce the energetic cost of body temperature maintenance under fasting. By analyzing ultradian regulation of body temperature, we describe a means by which an endotherm appears to lower thermoregulatory costs in response to the combined stressors of cold and fasting.本研究旨在探究鸟类在面临两种常见应激源——寒冷与禁食——时的体温调节响应。将可长期、精准采集体内体温的记录设备植入适应寒冷环境（5℃）或热中性环境（thermoneutrality，25℃）的雏鸭砂囊中。随后将实验动物分为三个均等的四天周期开展观测：自由采食、禁食与复饲。通过分析体温的日节律以及短期（或称超日节律（ultradian））变化，我们发现：处于热中性环境的雏鸭在禁食时，其每日体温调节参数仅出现轻微下降，但禁食期间其关键血管性热交换位点的体表温度会降低。而适应寒冷环境的雏鸭则表现出相反的变化：禁食期间其体温的短期波动显著降低，长期波动却有所升高。该现象可使适应寒冷环境的雏鸭在禁食状态下降低体温维持所需的能量成本。通过分析体温的超日节律调控，我们揭示了恒温动物（endotherm）应对寒冷与禁食双重应激源时，降低体温调节成本的一种调控路径。