Field Research Station at Fort Missoula, Division of Biological Sciences, University of Montana, Missoula, United States.
ZatzWorks Inc, Homer, United States.
Elife. 2020 Jun 30;9:e55774. doi: 10.7554/eLife.55774.
Birds that use their wings for 'flight' in both air and water are expected to fly poorly in each fluid relative to single-fluid specialists; that is, these jacks-of-all-trades should be the masters of none. Alcids exhibit exceptional dive performance while retaining aerial flight. We hypothesized that alcids maintain efficient Strouhal numbers and stroke velocities across air and water, allowing them to mitigate the costs of their 'fluid generalism'. We show that alcids cruise at Strouhal numbers between 0.10 and 0.40 - on par with single-fluid specialists - in both air and water but flap their wings ~ 50% slower in water. Thus, these species either contract their muscles at inefficient velocities or maintain a two-geared muscle system, highlighting a clear cost to using the same morphology for locomotion in two fluids. Additionally, alcids varied stroke-plane angle between air and water and chord angle during aquatic flight, expanding their performance envelope.
鸟类在空气和水中都使用翅膀进行“飞行”，预计在每种流体中的飞行表现都不如单一流体专家；也就是说，这些样样皆通的鸟类应该没有一项是精通的。海雀在保留空中飞行能力的同时，表现出了非凡的潜水能力。我们假设海雀在空气和水中都能保持高效的斯特劳哈尔数和冲程速度，从而减轻它们“流体通用性”的代价。我们发现，海雀在空气和水中的巡游斯特劳哈尔数在 0.10 到 0.40 之间——与单一流体专家相当——但在水中的翅膀拍动速度慢了约 50%。因此，这些物种要么以低效的速度收缩肌肉，要么维持一种双齿轮肌肉系统，这突出了在两种流体中使用相同的形态进行运动的明显代价。此外，海雀在空气和水中改变了冲程平面角度，在水中飞行时改变了翼弦角度，扩大了它们的性能范围。
