Cornell University Museum of Vertebrates, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA.
Proc Biol Sci. 2010 Mar 22;277(1683):835-41. doi: 10.1098/rspb.2009.1576. Epub 2009 Nov 11.
Male Club-winged Manakins, Machaeropterus deliciosus (Aves: Pipridae), produce a sustained tonal sound with specialized wing feathers. The fundamental frequency of the sound produced in nature is approximately 1500 Hz and is hypothesized to result from excitation of resonance in the feathers' hypertrophied shafts. We used laser Doppler vibrometry to determine the resonant properties of male Club-winged Manakin's wing feathers, as well as those of two unspecialized manakin species. The modified wing feathers exhibit a response peak near 1500 Hz, and unusually high Q-values (a measure of resonant tuning) for biological objects (Q up to 27). The unmodified wing feathers of the Club-winged Manakin do not exhibit strong resonant properties when measured in isolation. However, when measured still attached to the modified feathers (nine feathers held adjacent by an intact ligament), they resonate together as a unit near 1500 Hz, and the wing produces a second harmonic of similar or greater amplitude than the fundamental. The feathers of the control species also exhibit resonant peaks around 1500 Hz, but these are significantly weaker, the wing does not resonate as a unit and no harmonics are produced. These results lend critical support to the resonant stridulation hypothesis of sound production in M. deliciosus.
雄性阔嘴凤头鹃（Aves： Pipridae）通过特殊的翅膀羽毛发出持续的音调声音。自然产生的声音的基频约为 1500 Hz，据推测是由于羽毛肥大轴的共振激发所致。我们使用激光多普勒测振仪来确定雄性阔嘴凤头鹃的翅膀羽毛以及两种非特化鹃形目物种的翅膀羽毛的共振特性。改良后的翅膀羽毛在 1500 Hz 附近显示出响应峰值，并且具有生物物体（Q 值高达 27）的异常高的 Q 值（衡量共振调谐的指标）。阔嘴凤头鹃的未改良翅膀羽毛在单独测量时没有显示出强烈的共振特性。但是，当与改良的羽毛（由完整的韧带相邻保持的九个羽毛）一起测量时，它们会在 1500 Hz 附近一起作为一个单元共振，并且翅膀会产生与基频相似或更大幅度的二次谐波。对照物种的羽毛也在 1500 Hz 左右显示出共振峰值，但这些峰值明显较弱，翅膀不会作为一个单元共振，也不会产生谐波。这些结果为 M. deliciosus 声音产生的共振摩擦假说提供了关键支持。
