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The metabolic cost of breathing at rest has never been successfully measured in birds, but has been hypothesized to be higher than in mammals of a similar size because of the rocking motion of the avian sternum being encumbered by the pectoral flight muscles. To measure the cost and work of breathing, and to investigate whether species resident at high altitude exhibit morphological or mechanical changes that alter the work of breathing, we studied 11 species of waterfowl: five from high altitudes (>3000 m) in Peru, and six from low altitudes in Oregon, USA. Birds were anesthetized and mechanically ventilated in sternal recumbency with known tidal volumes and breathing frequencies. The work done by the ventilator was measured, and these values were applied to the combinations of tidal volumes and breathing frequencies used by the birds to breathe at rest. We found the respiratory system of high-altitude species to be of a similar size, but consistently more compliant than that of low altitude sister taxa, although this did not translate to a significantly reduced work of breathing. The metabolic cost of breathing was estimated to be between 1 and 3% of basal metabolic rate, as low or lower than estimates for other groups of tetrapods.

Item Type:	Refereed Article
Keywords:	avian respiratory system, compliance, hypoxia, pulmonary mechanics, waterfowl, work of breathing
Research Division:	Biological Sciences
Research Group:	Zoology
Research Field:	Animal physiological ecology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the biological sciences
UTAS Author:	Frappell, PB (Professor Peter Frappell)
ID Code:	123503
Year Published:	2017
Web of Science® Times Cited:	12
Deposited By:	Ecology and Biodiversity
Deposited On:	2018-01-10
Last Modified:	2018-05-30
Downloads:	133 View Download Statistics