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Hummingbird maneuvering performance : aerodynamic mechanisms and physiological constraints Segre, Paolo S.

Abstract

The ability of a bird to maneuver in flight can determine its success at avoiding predators, catching prey, and other critical behaviors. Highly maneuverable animals, such as hummingbirds, are capable of diverse behaviors but it is unknown how their maneuvering is constrained by wing motion, wing morphology, and muscle capacity. The purpose of this dissertation was to determine: 1) if hummingbird wings create independent wakes; 2) if independent wingbeat kinematics are used to control maneuvers; and 3) how maneuverability is limited by intrinsic features, such as wing morphology, body mass, and physical properties of the air, versus facultative capacity, such as muscle power. The goal of chapter two was to determine if hummingbirds produce single or bilateral vortex wakes using flow visualization. The goal of chapter three was to determine if sustained maneuvers can be controlled by orienting the wings independently of the body. I tested this hypothesis by filming the three dimensional kinematics of a hummingbird feeding from a translating feeder. The goal of chapter four was to determine if the ability to perform voluntary maneuvers was associated with intrinsic or facultative features. I addressed this question using a tracking system to record a large data set of voluntary flight trajectories, with independent measurements of individual morphology and maximum muscle capacity. The goal of chapter five was to determine if maneuvering performance declines with increasing elevation and, if so, whether changes in oxygen availability or air density are most responsible. I addressed these questions by measuring maneuvering performance across elevation and in an airtight chamber with gas manipulations. Collectively, my results indicate that hummingbirds have wings that operate with a high degree of independence and that this feature influences their precision and control. Voluntary maneuvers at low elevation are primarily influenced by facultative capacity, specifically burst power, and to a lesser extent by intrinsic limits, specifically wing aspect ratio. At higher elevations, maneuvering performance declines due to decreases in air density. This research demonstrates that the remarkable maneuverability of hummingbirds derives from their ability to control their wings independently and from high muscle power reserves for generating aerodynamic force. Supplementary video material is available at: http://hdl.handle.net/2429/54568

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Attribution-NonCommercial-NoDerivs 2.5 Canada