Ennos A, Hickson J, Roberts A
J Exp Biol. 1995;198(Pt 5):1219-28. doi: 10.1242/jeb.198.5.1219.
The functional morphology of feather vanes was examined by combining morphological examination with mechanical tests. A geometrical model was derived which related the in-plane behaviour of the vane to the orientation of the barbs and barbules. This predicted that the small branching angles of both barbs and proximal barbules should result in a vane which is easier to move distally than proximally. These predictions were verified by mechanical tests on primary and secondary feathers of the pigeon Columba livia. A further prediction, that the inclination of the barbs' cross section should make the vanes more resistant to forces from below than those from above, was also confirmed by mechanical tests. Differences in the mechanical behaviour of feathers are related to differences in their morphology and function. The vanes of outer primaries are more resistant to out-of-plane forces than those of the inner primaries and secondaries, particularly towards their tip, a property which will help them withstand the larger aerodynamic forces to which they may be subjected in flight. The outermost primary vane also showed the least asymmetry to out-of-plane forces as a result of the more vertical orientation of its barbs. This may help it to act as a reversible aerofoil during take-off.
通过将形态学检查与力学测试相结合，对羽片的功能形态进行了研究。得出了一个几何模型，该模型将羽片的面内行为与羽枝和小羽枝的方向联系起来。这预测羽枝和近端小羽枝的小分支角度应导致羽片向远端移动比向近端移动更容易。这些预测通过对家鸽（Columba livia）初级和次级羽毛的力学测试得到了验证。另一个预测，即羽枝横截面的倾斜度应使羽片对来自下方的力比来自上方的力更具抵抗力，也通过力学测试得到了证实。羽毛力学行为的差异与其形态和功能的差异有关。外侧初级飞羽的羽片比内侧初级飞羽和次级飞羽的羽片更能抵抗面外作用力，尤其是在羽片尖端，这一特性将有助于它们承受飞行中可能受到的更大空气动力。最外侧的初级羽片由于其羽枝更垂直的方向，在面外作用力方面也表现出最小的不对称性。这可能有助于它在起飞时充当可逆翼型。
