Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Richmond, NSW, 2753, Australia.
Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Richmond, NSW, 2753, Australia; School of Science, Western Sydney University, Hawkesbury campus, Richmond, NSW, 2753, Australia.
J Therm Biol. 2024 Feb;120:103792. doi: 10.1016/j.jtherbio.2024.103792. Epub 2024 Jan 28.
Small birds and mammals face similar energetic challenges, yet use of torpor to conserve energy while resting is considered less common among birds, especially within the most specious order Passeriformes. We conducted the first study to record the natural thermoregulatory physiology of any species from the family Hirundinidae, which we predicted would use torpor because of their specialised foraging by aerial pursuit of flying insects, that are less active during cold or windy weather. We used temperature telemetry on wild-living welcome swallows (Hirundo neoxena, 13 to 17 g) and found that skin temperature declined during nightly resting by an average by 5 °C, from daytime minima of 41.0 ± 0.8 °C to nightly minima of 36.3 ± 0.8 °C, and by a maximum of 8 °C to a minimum recorded skin temperature of 32.0 °C. The extent of reduction in skin temperature was greater on cold nights and following windy daytime (foraging) periods. Further, we found that transmitters glued directly to the skin between feather tracts (i.e., an apterium) provided a less variable and probably also more accurate reflection of body temperature than transmitters applied over closely trimmed feathers. A moderate decrease in skin temperature, equivalent to shallow torpor, would provide energy savings during rest. Yet, deeper torpor was not observed, despite a period of extreme rainfall that presumedly decreased foraging success. Further studies are needed to understand the resting thermoregulatory energetics of swallows under different environmental conditions. We advocate the importance of measuring thermal biology in wild-living birds to increase our knowledge of the physiology and ecological importance of torpor among passerine birds.
小型鸟类和哺乳动物面临着相似的能量挑战，但在休息时使用蛰伏来节约能量的情况在鸟类中被认为不太常见，尤其是在最具多样性的雀形目鸟类中。我们进行了首次记录家燕科（ Hirundinidae ）任何物种自然体温调节生理学的研究，我们预测它们会使用蛰伏，因为它们专门通过空中追逐飞行昆虫觅食，而这些昆虫在寒冷或刮风的天气中活动较少。我们使用温度遥测技术对野生的欢迎燕（ Hirundo neoxena ，13 至 17 克）进行了研究，发现它们在夜间休息时皮肤温度平均下降了 5°C，从白天的最低值 41.0°C±0.8°C 下降到夜间的最低值 36.3°C±0.8°C ，最大降幅达到 8°C ，记录到的皮肤最低温度为 32.0°C。在寒冷的夜晚和刮风的白天（觅食期）之后，皮肤温度的降低幅度更大。此外，我们发现，直接粘贴在羽毛之间的皮肤（即无羽区）上的传感器提供的体温变化比粘贴在修剪过的羽毛上的传感器更小、更准确。皮肤温度适度下降，相当于浅层蛰伏，将在休息时提供能量节约。然而，尽管经历了一场可能降低觅食成功率的极端降雨，我们仍未观察到更深层次的蛰伏。需要进一步的研究来了解不同环境条件下燕子的休息体温调节能量学。我们主张在野生鸟类中测量热生物学的重要性，以增加我们对蛰伏在雀形目鸟类中的生理学和生态重要性的认识。
