Year of Award


Document Type


Degree Type

Doctor of Philosophy (PhD)

Degree Name

Organismal Biology, Ecology, and Evolution

Department or School/College

Division of Biological Sciences

Committee Chair

Bret W. Tobalske

Commitee Members

Christopher J. Clark, Erick Greene, Douglas J. Emlen, H. Arthur Woods


aerodynamics, flight, flutter, morphology, sonation, wing sounds


University of Montana


The feathers of the wing that power flight in birds (the remiges) are morphologically constrained by the demands of aerial locomotion, but peculiar morphologies exist in many taxa in spite of these constraints. In the family Columbidae (pigeons and doves) in particular, we found that atypical remex morphologies have evolved dozens of times and occur in over a third of all species in the family. In members of the genus Columbina, we tested the sound-producing abilities of modified P7 feathers and determined that they are sonations that serve a signalling function during flight. In 56 species we identified a highly-attenuated outermost primary feather (P10) that improves aerodynamic performance by reducing drag in emulated gliding and flapping, much like slotted primaries in other birds. During emulated slow flapping flight, this feather dramatically improves performance at moderate angles of attack, much like the alula of passerines. Lastly, in the Rock Pigeon (Columba livia), we tested the aeroacoustic and aerodynamic function of its typical feathers and determined that subtle morphological changes to the barbs of P10 allow it to sonate, but at a cost to aerodynamic performance. Asymmetrical feathers specialized for aerial locomotion were a critical evolutionary transition in the avian lineage. Understanding how and why some taxa evolve feathers that deviate from, or entirely circumvent the constraints of aerial locomotion elucidates the mechanisms by which Aves has diversified. Furthermore, through investigating the mechanisms by which “occasional and accidental sounds” (e.g. the sounds of feathers flapping) become communicative signals we are probing the evolutionary origins of acoustic communication, an endeavor which may even influence our understanding of the evolution of human language.



© Copyright 2019 Robert Lawrence Niese