549: Courting Bird Sings with Stridulating Wing Feathers

Courting Bird Sings with Stridulating Wing Feathers -- Bostwick and Prum 309 (5735): 736 -- Science:

In birds and other vertebrates, most acoustic signals are produced pneumatically by moving air through a vocal apparatus. Here we describe a unique mechanism used to produce a tonal acoustic signal in vertebrates. Video recordings of the courtship displays of male Club-winged Manakins, Machaeropterus deliciosus, reveal that males produce sustained harmonic tones through interactions among oscillating secondary wing feathers. This mechanism of sound production shows morphological and mechanistic convergence with arthropod stridulation. Intersexual selection for production of a nonvocal courtship song has led to major morphological, functional, and likely physiological modifications in the wing of this flying bird.

Bostwick did her PhD under Prum here at KU. In her thesis defense, she made the point that many morphologists had long seen the wing as a purely functional object, that selection couldn't act on any other aspect of it.

Her research shows that the wing morphology and feather morphology in this species have changed to allow it to produce noise in a courtship display.

By examining close relatives, Bostwick (and Prum before her) showed that the display has evolved and that various structures, including the syrinx (song box) have evolved along with the display. The constraints of courtship displays caused the wing to evolve in different ways, away from some teleological "function," and toward the practical uses of the bird.