Hummingbirds and nectar bats are the only vertebrates that are specialized for hovering in front of flowers to forage nectar. How their aerodynamic performance compares is, however, unclear. To hover, hummingbirds consistently generate about a quarter of the vertical aerodynamic force required to support their body weight during the upstroke. In contrast, generalist birds in slow hovering flight generate little upstroke weight support. We report that nectar bats also generate elevated weight support during the upstroke compared to generalist bats. Comparing 20 Neotropical species, we show how nectarivorous birds and bats converged on this ability by inverting their respective feathered and membrane wings more than species with other diets. However, while hummingbirds converged on an efficient horizontal wingbeat to mostly generate lift, bats rely on lift and drag during the downstroke to fully support their body weight. Furthermore, whereas the ability of nectar bats to aerodynamically support their body weight during the upstroke is elevated, it is much smaller than that of hummingbirds. Bats compensate by generating more aerodynamic weight support during their extended downstroke. Although, in principle, it requires more aerodynamic power to hover using this method, bats have adapted by evolving much larger wings for their body weight. Therefore, the net aerodynamic induced power required to hover is similar among hummingbirds and bats per unit body mass. This mechanistic insight into how feathered wings and membrane wings ultimately require similar aerodynamic power to hover may inform analogous design trade-offs in aerial robots.

中文翻译：

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新热带蜂鸟与蝙蝠悬停性能的生物力学。

蜂鸟和花蜜蝙蝠是唯一专门在花前盘旋采集花蜜的脊椎动物。然而，它们的空气动力学性能如何比较尚不清楚。为了悬停，蜂鸟在上冲时始终产生支撑其体重所需的大约四分之一的垂直空气动力。相比之下，多面手鸟类在缓慢盘旋飞行时几乎不会产生上冲重量支撑。我们报告说，与通才蝙蝠相比，花蜜蝙蝠在上冲程中也会产生更高的重量支撑。通过比较 20 个新热带物种，我们展示了食蜜鸟类和蝙蝠如何通过比其他饮食物种更多地翻转各自的羽毛和膜翅来实现这种能力。然而，蜂鸟集中在有效的水平振翼上以主要产生升力，而蝙蝠在下划过程中依靠升力和阻力来完全支撑其体重。此外，虽然花蜜蝙蝠在上冲过程中通过空气动力学支撑其体重的能力有所提高，但它比蜂鸟小得多。球棒通过在延长的下击过程中产生更多的空气动力学重量支撑来进行补偿。尽管从原则上讲，使用这种方法盘旋需要更多的空气动力，但蝙蝠已经适应了这种方法，根据其体重进化出了更大的翅膀。因此，蜂鸟和蝙蝠每单位体重悬停所需的净空气动力感应功率相似。这种对羽毛翼和膜翼最终如何需要类似的空气动力来悬停的机械见解可能会为空中机器人的类似设计权衡提供信息。