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Water and Energy Limitations on Flight Duration in Small Migrating Birds

Water and Energy Limitations on Flight Duration in Small Migrating Birds Abstract We examined the physiological limitations to flight duration in small migrating birds with a computer-simulation model. Given preflight body mass, fat and water contents, and flight-path meteorological data, we calculated water and energy budgets and possible flight time. The model can be applied to birds of any size that migrate by flapping flight. As an example, we simulated the flight of small Palearctic passerines (body mass = 10 g) during their annual migration over the Sahara desert. Sensitivity analysis of model input variables indicated that oxygen extraction and expired air temperature are the most important phys¬iological variables in a bird's water budget and can profoundly influence flight duration. This manifests the importance of: (1) efficient cooling in the nasal passages of flying birds; and (2) the choice of flight altitude (which affects both ambient air temperature and expired air temperature). The model predicted that: (1) Prior to migration, these birds must have stored fat comprising at least 22% of their initial body mass; otherwise, they cannot complete their journey. (2) In relatively fat birds (stored fat >0.22 body mass), dehydration rather than energy will limit flight duration. (3) Birds should fly at an altitude not exceeding 1,000 m to cross the Sahara successfully. (4) Even in low-flying fat birds, flight duration will be limited by their stringent water budget. The model further predicted that small passerines cannot cross the Sahara in a 30- to 40-h nonstop flight, as commonly accepted, but should confine flying to the cooler hours (i.e. nights) and rest during the day in order to avoid elevated rates of water loss due to higher ambient air temperatures. Available data and observations of birds trapped at stopover sites in the Sahara support these predictions. This content is only available as a PDF. Copyright © 1992 by American Ornithological Society Inc. All rights reserved. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Auk: Ornithological Advances Oxford University Press

Water and Energy Limitations on Flight Duration in Small Migrating Birds

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References (36)

Publisher
Oxford University Press
Copyright
Copyright © 1992 by American Ornithological Society Inc. All rights reserved.
ISSN
0004-8038
eISSN
1938-4254
DOI
10.2307/4088195
Publisher site
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Abstract

Abstract We examined the physiological limitations to flight duration in small migrating birds with a computer-simulation model. Given preflight body mass, fat and water contents, and flight-path meteorological data, we calculated water and energy budgets and possible flight time. The model can be applied to birds of any size that migrate by flapping flight. As an example, we simulated the flight of small Palearctic passerines (body mass = 10 g) during their annual migration over the Sahara desert. Sensitivity analysis of model input variables indicated that oxygen extraction and expired air temperature are the most important phys¬iological variables in a bird's water budget and can profoundly influence flight duration. This manifests the importance of: (1) efficient cooling in the nasal passages of flying birds; and (2) the choice of flight altitude (which affects both ambient air temperature and expired air temperature). The model predicted that: (1) Prior to migration, these birds must have stored fat comprising at least 22% of their initial body mass; otherwise, they cannot complete their journey. (2) In relatively fat birds (stored fat >0.22 body mass), dehydration rather than energy will limit flight duration. (3) Birds should fly at an altitude not exceeding 1,000 m to cross the Sahara successfully. (4) Even in low-flying fat birds, flight duration will be limited by their stringent water budget. The model further predicted that small passerines cannot cross the Sahara in a 30- to 40-h nonstop flight, as commonly accepted, but should confine flying to the cooler hours (i.e. nights) and rest during the day in order to avoid elevated rates of water loss due to higher ambient air temperatures. Available data and observations of birds trapped at stopover sites in the Sahara support these predictions. This content is only available as a PDF. Copyright © 1992 by American Ornithological Society Inc. All rights reserved.

Journal

Auk: Ornithological Advances – Oxford University Press

Published: Apr 1, 1992

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