Aerodynamics, biomechanics and neuromuscular control of avian flight

This dissertation employed several different approaches to understand how the aerodynamics, biomechanics and neuromuscular control of avian flight mutually influence one another and help to explain the observed flight behavior of birds. Avian flight aerodynamics has most frequently been studied from a theoretical perspective and less often based on experimental work. Of these latter, a smaller number of studies have examined avian flight physiology, but few have approached the control mechanisms that underlie flight behavior. Despite these representing traditionally separate approaches and fields, these different areas can inform one another, and conclusions drawn from research at one level must be compatible with functional requirements at other levels of the entire organism.; My dissertation consisted of four linked projects, the first of which considered the aerodynamic consequences of flight across a range of speeds. My systematic 3D-kinematic and aerodynamic evaluation of flight across a range of speeds in cockatiels (Nymphicus hollandicus) and turtle doves (Streptopelia risoria) showed that birds do change aerodynamic gaits with speed, but that this may occur without the underlying shift in neuromuscular control which characterizes gait change in terrestrial locomotion (Chapter 2). Next (Chapter 3) I used an aerodynamic model in combination with in vivo recordings of flight muscle force and length change to measure the power requirements of cockatiels flying across a range of speeds to examine how power output is controlled by different motor properties of the flight muscles and variation in stimulation provided by the nervous system. Next (Chapter 4) I examined the within-wingbeat variation in aerodynamic force generation for comparison with both the timing of flight muscle force generation and the parameters typically used as inputs to aerodynamic models of avian flight. Finally (Chapter 5), I examined the neuromuscular basis for an aerodynamic model of maneuvering control and demonstrated that a pre-existing model for maneuvering flight in pigeons is not compatible with the recorded neuromuscular activity I observed in cockatoos (Cacatuidae). Instead, my neuromuscular recordings suggest an alternative aerodynamic model of maneuvering control based on changes in wing orientation, rather than flapping velocity.