鸽子的飞行方式与直升机类似（图片来源：Ivo Ros）
生活在城市中的鸽子或许被嘲笑为就像只会飞的老鼠，然而在空中，它们更像是直升飞机。这项关于鸽子在空中如何转向的新研究的重要结果发表在11月28日出版的美国《国家科学院院刊》上。
美国哈佛大学康克德野外台站的鸟类学家Ivo G. Ros和同事在一座室内停车场用网围住了一些常见的鸽子（Columba livia），并在它们于一个角落缓慢转向时用高速摄像机对其进行了拍摄。
根据这些录像，研究人员随后计算了由鸟类所产生的保持它们在空中停留并运动的气动力。
与一枚火箭简单地旋转其喷气机不同，一只鸽子并不会通过改变其所产生的力量相对于身体的方向来转向。
而事实上，这种飞鸟会通过旋转整个身体，主要是倾斜翅膀转向来调整它们的力量。
而一架直升飞机也会采用相同的倾斜策略，以降低它的噪音并加速前进。
这项研究同时发现，转向的鸽子向上所产生的升力居然可以媲美超级高空杂技演员蜂鸟所产生的升力——这对于鸟类世界的笑柄来说还不赖。
doi:10.1073/pnas.1107519108
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Pigeons steer like helicopters and generate down- and upstroke lift during low speed turns
Ivo G. Rosa,1, Lori C. Bassmanb, Marc A. Badgerb, Alyssa N. Piersonb, and Andrew A. Biewenera
Turning is crucial for animals, particularly during predator–prey interactions and to avoid obstacles. For flying animals, turning consists of changes in (i) flight trajectory, or path of travel, and (ii) body orientation, or 3D angular position. Changes in flight trajectory can only be achieved by modulating aerodynamic forces relative to gravity. How birds coordinate aerodynamic force production relative to changes in body orientation during turns is key to understanding the control strategies used in avian maneuvering flight. We hypothesized that pigeons produce aerodynamic forces in a uniform direction relative to their bodies, requiring changes in body orientation to redirect those forces to turn. Using detailed 3D kinematics and body mass distributions, we examined net aerodynamic forces and body orientations in slowly flying pigeons (Columba livia) executing level 90° turns. The net aerodynamic force averaged over the downstroke was maintained in a fixed direction relative to the body throughout the turn, even though the body orientation of the birds varied substantially. Early in the turn, changes in body orientation primarily redirected the downstroke aerodynamic force, affecting the bird’s flight trajectory. Subsequently, the pigeon mainly reacquired the body orientation used in forward flight without affecting its flight trajectory. Surprisingly, the pigeon’s upstroke generated aerodynamic forces that were approximately 50% of those generated during the downstroke, nearly matching the relative upstroke forces produced by hummingbirds. Thus, pigeons achieve low speed turns much like helicopters, by using whole-body rotations to alter the direction of aerodynamic force production to change their flight trajectory.
