Brigham R M, Körtner G, Maddocks T A, Geiser F
Zoology School of Biological Sciences, University of New England, Armidale. New South Wales, Australia.
Physiol Biochem Zool. 2000 Sep-Oct;73(5):613-20. doi: 10.1086/317755.
With the exception of some data for common poorwills (Phalaenoptilus nuttallii) and anecdotal reports for a few other species, knowledge about the use of torpor by free-ranging birds is limited. Our study was designed to assess the use of torpor by free-ranging Australian owlet-nightjars (Aegotheles cristatus). We selected this species for study because of their relatively small body size (50 g), arthropod diet, nocturnal sedentary nature, taxonomic affiliation with other birds for whom the use of torpor is well documented, use of cavity roosts, and because of the cold winter (mean July minimum ambient temperature [T(a)] of approximately 0 degrees C) in the study area. We tracked 12 owlet-nightjars carrying temperature-sensitive transmitters for a total of 906 bird-days (range of 15-115 d per individual). Five different individuals entered torpor on 96 d in total. Torpor bouts occurred only between May 8 and September 8, the coldest period of the year. The lowest skin temperature (T(skin)) recorded for any bird was 19.6 degrees C, and the lowest core temperature was 22.4 degrees C. Surprisingly, torpor was rarely used at night because birds usually foraged then. Instead, torpor typically began near dawn, even on cold nights. Torpor bouts beginning at dawn lasted approximately 4 h. On 36% of days when torpor was used at dawn, birds reentered torpor later in the day. Torpor was not used during the breeding season, but this period also corresponds to the warm part of the year. There were no distinct daily minimum, maximum, or mean T(a) thresholds that could be used to reliably distinguish days when dawn torpor was used from those when it was not, although torpor was commonly employed when daily minimum T(a) fell below 3.9 degrees C. Our results show that even though Australia is typically thought of as a warm continent, at least some of the avifauna use torpor as a regular means of saving energy. We hypothesise that the reasons for this species' use of torpor include its ability to remain active all night foraging, either for terrestrial arthropods while walking or for flying insects taken on the wing, and/or its habit of roosting in cavities, which allows them to remain hidden in the daytime.
除了一些关于普通夜鹰（Phalaenoptilus nuttallii）的数据以及少数其他物种的轶事报道外，关于自由放养鸟类使用蛰伏的知识非常有限。我们的研究旨在评估自由放养的澳大利亚蟆口鸱（Aegotheles cristatus）对蛰伏的使用情况。我们选择这个物种进行研究，是因为它们体型相对较小（50克），以节肢动物为食，具有夜间久坐不动的习性，与其他有充分文献记载使用蛰伏的鸟类有分类学关联，使用树洞栖息，还因为研究区域冬季寒冷（7月平均最低环境温度[T(a)]约为0摄氏度）。我们追踪了12只携带温度敏感发射器的蟆口鸱，总共记录了906个鸟日（每只个体的记录时长在15 - 115天之间）。共有5只不同的个体总共在96天进入了蛰伏状态。蛰伏期仅发生在5月8日至9月8日，即一年中最冷的时期。记录到的任何一只鸟的最低皮肤温度（T(skin)）为19.6摄氏度，最低核心温度为22.4摄氏度。令人惊讶的是，它们很少在夜间进入蛰伏，因为鸟类通常在夜间觅食。相反，蛰伏通常在黎明时分开始，即使是在寒冷的夜晚。从黎明开始的蛰伏期持续约4小时。在黎明时进入蛰伏的日子里，有36%的情况是鸟类在当天晚些时候再次进入蛰伏。繁殖季节不使用蛰伏，但这个时期也是一年中较温暖的时段。虽然当每日最低T(a)降至3.9摄氏度以下时通常会使用蛰伏，但并没有明显的每日最低、最高或平均T(a)阈值可用于可靠地区分使用黎明蛰伏的日子和不使用的日子。我们的研究结果表明，尽管澳大利亚通常被认为是一个温暖的大陆，但至少有一些鸟类将蛰伏作为一种常规的节能方式。我们推测该物种使用蛰伏的原因包括其能够整夜活跃觅食，既可以在地面行走时捕食陆生节肢动物，也可以在空中捕食飞行昆虫，和/或其在树洞中栖息的习性，这使得它们在白天能够隐藏起来。
