Douglas Tegan K, Cooper Christine E, Withers Philip C
Department of Environment and Agriculture, Curtin University, Bentley, WA 6845, Australia.
Department of Environment and Agriculture, Curtin University, Bentley, WA 6845, Australia
J Exp Biol. 2017 Apr 1;220(Pt 7):1341-1349. doi: 10.1242/jeb.154633.
It is unclear whether torpor really is uncommon amongst passerine birds. We therefore examined body temperature and thermoregulatory strategies of an Austral passerine, the white-browed babbler (), which has characteristics related to a high probability of torpor use; it is a sedentary, insectivorous, cooperative breeding species, which we studied during winter in a temperate habitat. Wild, free-living babblers maintained normothermy overnight, even at sub-zero ambient temperatures, with a mean minimum body temperature of 38.5±0.04°C that was independent of minimum black bulb temperature. Physiological variables measured in the laboratory revealed that babblers had a low basal metabolic rate and evaporative water loss, but their body temperature and thermal conductance were typical of those of other birds and they had a typical endothermic response to low ambient temperature. Huddling yielded significant energy savings at low temperatures and a roost nest created a microclimate that buffered against low temperatures. Low basal energy requirements, communal roosting and the insulation of a roost nest confer sufficient energetic benefits, allowing babblers to meet energy requirements without resorting to heterothermia, even in their depauperate, low-productivity landscape, suggesting that passerine birds use alternatives to torpor to balance their energy budgets when possible.
目前尚不清楚蛰伏现象在雀形目鸟类中是否真的不常见。因此，我们研究了一种澳大利亚雀形目鸟类——白眉弯嘴鹛（学名：Pomatostomus superciliosus）的体温和体温调节策略，该物种具有较高的蛰伏可能性；它是一种定居性、食虫性、合作繁殖的物种，我们在冬季于温带栖息地对其进行了研究。野生的自由生活的弯嘴鹛即使在环境温度低于零度的情况下，夜间仍能维持正常体温，平均最低体温为38.5±0.04°C，且与最低黑球温度无关。在实验室测量的生理变量表明，弯嘴鹛的基础代谢率和蒸发失水量较低，但其体温和热传导与其他鸟类典型特征相似，并且对低温具有典型的恒温动物反应。在低温时，拥挤抱团能显著节省能量，而栖息巢营造了一个缓冲低温的微气候环境。较低的基础能量需求、群居栖息以及栖息巢的保温作用带来了足够的能量益处，使得弯嘴鹛即使在其贫瘠、低生产力的栖息地中，也能够在不采用异温性的情况下满足能量需求，这表明雀形目鸟类在可能的情况下会使用蛰伏之外的其他方式来平衡其能量预算。
