Meeting Abstract
The sounds produced by the wings of Rock Pigeons have intrigued naturalists for centuries. Many have suggested that the tonal elements of these sounds may be signals or sonations of alarm, but spurious tonal sounds are produced passively by the flight feathers of almost all birds when they aeroelastically flutter. Before we can conclude that tonal wing sounds are sonations, we must identify some characteristic of the feathers of Rock Pigeons that is specifically adapted for sound production rather than flight. We must also provide evidence to suggest that this morphology is necessary for in vivo sound production and is sufficient to replicate in vivo sounds alone. Our investigations revealed unique structural characteristics of a small portion of the inner vane on the outermost primary feather (P10) of Rock Pigeon wings that facilitates aeroelastic flutter above certain velocities. These same velocities were insufficient to activate flutter in other feathers. We were able to successfully silence the tonal wing sounds of live birds through manipulating this region of P10 to increase its stiffness, thus preventing flutter. Laboratory experiments on isolated feathers indicated that tones produced by flutter in this region of P10 nearly match those produced in vivo, and that the activation of flutter in P10 results in a significant decrease in the feather’s aerodynamic force-producing ability (CR). This evidence suggests that the tonal sounds produced by P10 feathers are not purely incidental, opening the door to investigations of their communicative significance. Funding provided by NSF CMMI-1234737.
