Niese Robert L, Tobalske Bret W
Field Research Station at Fort Missoula, Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA Slater Museum of Natural History, Biology Department, University of Puget Sound, Tacoma, WA 98416, USA
Field Research Station at Fort Missoula, Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
J Exp Biol. 2016 Jul 15;219(Pt 14):2173-81. doi: 10.1242/jeb.131649. Epub 2016 May 13.
For centuries, naturalists have suggested that the tonal elements of pigeon wing sounds may be sonations (non-vocal acoustic signals) of alarm. However, spurious tonal sounds may be produced passively as a result of aeroelastic flutter in the flight feathers of almost all birds. Using mechanistic criteria emerging from recent work on sonations, we sought to: (1) identify characteristics of rock pigeon flight feathers that might be adapted for sound production rather than flight, and (2) provide evidence that this morphology is necessary for in vivo sound production and is sufficient to replicate in vivo sounds. Pigeons produce tonal sounds (700±50 Hz) during the latter two-thirds of each downstroke during take-off. These tones are produced when a small region of long, curved barbs on the inner vane of the outermost primary feather (P10) aeroelastically flutters. Tones were silenced in live birds when we experimentally increased the stiffness of this region to prevent flutter. Isolated P10 feathers were sufficient to reproduce in vivo sounds when spun at the peak angular velocity of downstroke (53.9-60.3 rad s(-1)), but did not produce tones at average downstroke velocity (31.8 rad s(-1)), whereas P9 and P1 feathers never produced tones. P10 feathers had significantly lower coefficients of resultant aerodynamic force (CR) when spun at peak angular velocity than at average angular velocity, revealing that production of tonal sounds incurs an aerodynamic cost. P9 and P1 feathers did not show this difference in CR These mechanistic results suggest that the tonal sounds produced by P10 feathers are not incidental and may function in communication.
几个世纪以来，博物学家一直认为鸽子翅膀声音的音调元素可能是警报的发声（非发声声学信号）。然而，几乎所有鸟类的飞羽因气动力弹性颤振可能会被动产生虚假的音调声音。利用近期关于发声研究中出现的机制标准，我们试图：（1）确定原鸽飞羽可能适合用于发声而非飞行的特征，以及（2）提供证据表明这种形态对于体内发声是必要的，并且足以复制体内声音。鸽子在起飞时每次向下冲程的后三分之二过程中会发出音调声音（700±50 Hz）。这些音调是在最外侧初级飞羽（P10）内羽片上一小片长而弯曲的羽枝区域发生气动力弹性颤振时产生的。当我们通过实验增加该区域的刚度以防止颤振时，活鸟发出的音调就消失了。分离的P10羽毛在以向下冲程的峰值角速度（53.9 - 6 0.3 rad s(-1)）旋转时足以复制体内声音，但在平均向下冲程速度（31.8 rad s(-1)）时不会产生音调，而P9和P1羽毛从未产生过音调。P10羽毛在以峰值角速度旋转时的合成气动力系数（CR）明显低于以平均角速度旋转时，这表明产生音调声音会产生气动力成本。P9和P1羽毛在CR上没有显示出这种差异。这些机制结果表明，P10羽毛产生的音调声音并非偶然，可能具有通讯功能。
