Biosciences, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
School of Earth and Environment, University of Leeds, Leeds, UK.
J R Soc Interface. 2024 Mar;21(212):20230591. doi: 10.1098/rsif.2023.0591. Epub 2024 Mar 20.
Turbulence is a widespread phenomenon in the natural world, but its influence on flapping fliers remains little studied. We assessed how freestream turbulence affected the kinematics, flight effort and track properties of homing pigeons (), using the fine-scale variations in flight height as a proxy for turbulence levels. Birds showed a small increase in their wingbeat amplitude with increasing turbulence (similar to laboratory studies), but this was accompanied by a reduction in mean wingbeat frequency, such that their flapping wing speed remained the same. Mean kinematic responses to turbulence may therefore enable birds to increase their stability without a reduction in propulsive efficiency. Nonetheless, the most marked response to turbulence was an increase in the variability of wingbeat frequency and amplitude. These stroke-to-stroke changes in kinematics provide instantaneous compensation for turbulence. They will also increase flight costs. Yet pigeons only made small adjustments to their flight altitude, likely resulting in little change in exposure to strong convective turbulence. Responses to turbulence were therefore distinct from responses to wind, with the costs of high turbulence being levied through an increase in the variability of their kinematics and airspeed. This highlights the value of investigating the variability in flight parameters in free-living animals.
紊流是自然界中普遍存在的现象，但它对扑翼飞行器的影响仍鲜有研究。我们评估了自由流紊流如何影响归巢鸽（Columba livia）的运动学、飞行努力和轨迹特性，使用飞行高度的细微变化作为紊流水平的替代物。鸟类的翅膀拍打幅度随紊流的增加而略有增加（类似于实验室研究），但平均翅膀拍打频率降低，从而保持相同的扑翼速度。因此，鸟类对紊流的平均运动学反应可能使它们在不降低推进效率的情况下提高稳定性。尽管如此，对紊流最明显的反应是翅膀拍打频率和幅度的可变性增加。这些运动学的拍间变化提供了对紊流的即时补偿。它们还会增加飞行成本。然而，鸽子只对飞行高度进行了微小的调整，可能导致暴露在强对流紊流中的变化很小。因此，对紊流的反应与对风的反应不同，通过增加运动学和空速的可变性来应对高紊流的成本。这突出了研究自由生活动物飞行参数变化的价值。
