Migratory birds are often not specifically adapted to arid conditions, yet several species travel across deserts during their journeys, and often have more or less short stopovers there. We investigated whether differences in thermoregulatory mechanisms, specifically evaporative cooling, explain the different behavior of three passerine species while stopping over in the Negev desert, Israel. We measured cutaneous water loss (CWL) under ambient conditions and the temperature of panting onset in an experimental setup. In addition, we performed behavioral observations of birds at a stopover site where we manipulated water availability. Blackcaps had slightly higher CWL at relatively low temperatures than Willow Warblers and Lesser Whitethroats. When considered relative to total body mass, however, Willow Warblers had the highest CWL of the three species. Blackcaps started panting at lower ambient temperature than the other two species. Taken together, these results suggest that Willow Warblers are the most efficient in cooling down their body, possibly with the cost of needing to regain water by actively foraging during their staging. Lesser Whitethroats had a similar pattern, which was reflected in their slightly higher levels of activity and drinking behavior when water was available. However, in general the behavior of migratory species was not affected by the availability of water, and they were observed drinking rather rarely. Our results indicate that differences in thermoregulatory mechanisms might be at the basis of the evolution of different stopover strategies of migratory birds while crossing arid areas such as deserts.

中文翻译：

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三种雀类鸟类秋季迁徙过程中蒸发水分流失及滞留行为

候鸟通常并不特别适应干旱条件，但有几个物种在旅途中穿越沙漠，通常或多或少在那里短暂停留。我们调查了体温调节机制的差异，特别是蒸发冷却，是否可以解释三种雀形目物种在以色列内盖夫沙漠停留时的不同行为。我们在实验装置中测量了环境条件下的皮肤水分流失 (CWL) 和喘气开始的温度。此外，我们在一个中途停留地点对鸟类进行了行为观察，在那里我们操纵了可用水量。Blackcaps 在相对较低的温度下的 CWL 略高于 Willow Warblers 和 Lesser Whitethroats。然而，当考虑到总体质量时，柳莺在三个物种中的 CWL 最高。Blackcaps 在比其他两个物种更低的环境温度下开始喘气。综上所述，这些结果表明柳莺在冷却身体方面最有效，可能需要通过在分期期间积极觅食来重新获得水分。较小的白喉有类似的模式，这反映在有水时它们的活动水平和饮酒行为略高。然而，一般来说，迁徙物种的行为不受水供应情况的影响，观察到它们很少喝水。我们的研究结果表明，体温调节机制的差异可能是候鸟穿越沙漠等干旱地区时不同中途停留策略演变的基础。Blackcaps 在比其他两个物种更低的环境温度下开始喘气。综上所述，这些结果表明柳莺在冷却身体方面最有效，可能需要通过在分期期间积极觅食来重新获得水分。较小的白喉有类似的模式，这反映在有水时它们的活动水平和饮酒行为略高。然而，一般来说，迁徙物种的行为不受水供应情况的影响，观察到它们很少喝水。我们的研究结果表明，体温调节机制的差异可能是候鸟穿越沙漠等干旱地区时不同中途停留策略演变的基础。Blackcaps 在比其他两个物种更低的环境温度下开始喘气。综上所述，这些结果表明柳莺在冷却身体方面最有效，可能需要通过在分期期间积极觅食来重新获得水分。较小的白喉有类似的模式，这反映在有水时它们的活动水平和饮酒行为略高。然而，一般来说，迁徙物种的行为不受水供应情况的影响，观察到它们很少喝水。我们的研究结果表明，体温调节机制的差异可能是候鸟穿越沙漠等干旱地区时不同中途停留策略演变的基础。