School of Biological Sciences M092, University of Western Australia, Crawley, Western Australia 6009, Australia.
Department of Environment and Agriculture, Curtin University, PO Box U1987, Perth, Western Australia 6847, Australia.
Proc Biol Sci. 2017 Nov 29;284(1867). doi: 10.1098/rspb.2017.1478.
Birds have many physiological characteristics that are convergent with mammals. In the light of recent evidence that mammals can maintain a constant insensible evaporative water loss (EWL) over a range of perturbing environmental conditions, we hypothesized that birds might also regulate insensible EWL, reflecting this convergence. We found that budgerigars () maintain EWL constant over a range of relative humidities at three ambient temperatures. EWL, expressed as a function of water vapour pressure deficit, differed from a physical model where the water vapour pressure deficit between the animal and the ambient air is the driver of evaporation, indicating physiological control of EWL. Regulating EWL avoids thermoregulatory impacts of varied evaporative heat loss; changes in relative humidity had no effect on body temperature, metabolic rate or thermal conductance. Our findings that a small bird can regulate EWL are evidence that this is a common feature of convergently endothermic birds and mammals, and may therefore be a fundamental characteristic of endothermy.
鸟类具有许多与哺乳动物相似的生理特征。鉴于最近有证据表明，哺乳动物可以在一系列环境条件变化下维持恒定的非感觉蒸发失水（EWL），我们假设鸟类也可能调节非感觉 EWL，反映出这种趋同进化。我们发现，虎皮鹦鹉在三个环境温度下的一系列相对湿度范围内维持 EWL 恒定。EWL 作为水蒸气压力差的函数，与动物和环境空气之间的水蒸气压力差是蒸发驱动力的物理模型不同，这表明 EWL 受到生理控制。调节 EWL 可以避免因蒸发散热变化而引起的体温调节影响；相对湿度的变化对体温、代谢率或热导率没有影响。我们发现，小鸟可以调节 EWL，这表明这是趋同温血动物鸟类和哺乳动物的共同特征，因此可能是温血动物的一个基本特征。
