Weger Matthias, Wagner Hermann
Institute of Zoology, RWTH Aachen University, Aachen, Germany.
J Anat. 2017 May;230(5):734-742. doi: 10.1111/joa.12595. Epub 2017 Mar 3.
Owls are known for the development of a silent flight. One conspicuous specialization of owl wings that has been implied in noise reduction and that has been demonstrated to change the aerodynamic behavior of the wing is a soft dorsal wing surface. The soft surface is a result of changes in the shape of feather barbs and barbules in owls compared with other bird species. We hypothesized that as the aerodynamic characteristics of a wing change along its chordwise and spanwise direction, so may the shape of the barbs and barbules. Therefore, we examined in detail the shapes of the barbs and barbules in chordwise and spanwise directions. The results showed changes in the shapes of barbs and barbules at the anterior and distal parts of the wing, but not at more posterior parts. The increased density of hook radiates at the distalmost wing position could serve to stiffen that vane part that is subject to the highest forces. The change of pennulum length in the anterior part of the wing and the uniformity further back could mean that a soft surface may be especially important in regions where flow separation may occur.
猫头鹰以其能够实现无声飞行而闻名。猫头鹰翅膀的一个显著特征是其柔软的背部表面，这一特征被认为与降低噪音有关，并且已被证明会改变翅膀的空气动力学行为。与其他鸟类相比，猫头鹰翅膀柔软表面的形成是由于羽毛羽枝和羽小枝形状的变化。我们推测，随着翅膀的空气动力学特性沿弦向和展向发生变化，羽枝和羽小枝的形状也可能会改变。因此，我们详细研究了羽枝和羽小枝在弦向和展向的形状。结果表明，翅膀前部和远端的羽枝和羽小枝形状发生了变化，但后部则没有。在翅膀最远端位置，钩状辐射密度的增加可能有助于加强该叶片部分承受最高力的能力。翅膀前部摆锤长度的变化以及向后的均匀性可能意味着，在可能发生气流分离的区域，柔软表面可能尤为重要。
