Mechanical Constraints on Flight at High Elevation Decrease Maneuvering Performance of Hummingbirds

Mechanical Constraints on Flight at High Elevation Decrease Maneuvering Performance of Hummingbirds High-elevation habitats offer ecological advantages including reduced competition, predation, and parasitism [1]. However, flying organisms at high elevation also face physiological challenges due to lower air density and oxygen availability [2]. These constraints are expected to affect the flight maneuvers that are required to compete with rivals, capture prey, and evade threats [3–5]. To test how individual maneuvering performance is affected by elevation, we measured the free-flight maneuvers of male Anna’s hummingbirds in a large chamber translocated to a high-elevation site and then measured their performance at low elevation. We used a multi-camera tracking system to identify thousands of maneuvers based on body position and orientation [6]. At high elevation, the birds’ translational velocities, accelerations, and rotational velocities were reduced, and they used less demanding turns. To determine how mechanical and metabolic constraints independently affect performance, we performed a second experiment to evaluate flight maneuvers in an airtight chamber infused with either normoxic heliox, to lower air density, or nitrogen, to lower oxygen availability. The hypodense treatment caused the birds to reduce their accelerations and rotational velocities, whereas the hypoxic treatment had no significant effect on maneuvering performance. Collectively, these experiments reveal how aerial maneuvering performance changes with elevation, demonstrating that as birds move up in elevation, air density constrains their maneuverability prior to any influence of oxygen availability. Our results support the hypothesis that changes in competitive ability at high elevations are the result of mechanical limits to flight performance [7]. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Current Biology Elsevier

Mechanical Constraints on Flight at High Elevation Decrease Maneuvering Performance of Hummingbirds

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Publisher
Elsevier
Copyright
Copyright © 2016 Elsevier Ltd
ISSN
0960-9822
D.O.I.
10.1016/j.cub.2016.10.028
Publisher site
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Abstract

High-elevation habitats offer ecological advantages including reduced competition, predation, and parasitism [1]. However, flying organisms at high elevation also face physiological challenges due to lower air density and oxygen availability [2]. These constraints are expected to affect the flight maneuvers that are required to compete with rivals, capture prey, and evade threats [3–5]. To test how individual maneuvering performance is affected by elevation, we measured the free-flight maneuvers of male Anna’s hummingbirds in a large chamber translocated to a high-elevation site and then measured their performance at low elevation. We used a multi-camera tracking system to identify thousands of maneuvers based on body position and orientation [6]. At high elevation, the birds’ translational velocities, accelerations, and rotational velocities were reduced, and they used less demanding turns. To determine how mechanical and metabolic constraints independently affect performance, we performed a second experiment to evaluate flight maneuvers in an airtight chamber infused with either normoxic heliox, to lower air density, or nitrogen, to lower oxygen availability. The hypodense treatment caused the birds to reduce their accelerations and rotational velocities, whereas the hypoxic treatment had no significant effect on maneuvering performance. Collectively, these experiments reveal how aerial maneuvering performance changes with elevation, demonstrating that as birds move up in elevation, air density constrains their maneuverability prior to any influence of oxygen availability. Our results support the hypothesis that changes in competitive ability at high elevations are the result of mechanical limits to flight performance [7].

Journal

Current BiologyElsevier

Published: Dec 19, 2016

References

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