Can birds do it too? Evidence for convergence in evaporative water loss regulation for birds and mammals

Birds have many physiological characteristics that are convergent with mammals. In the light of recent evidence that mammals can maintain a constant insensible evaporative water loss (EWL) over a range of perturbing environmental conditions, we hypothesized that birds might also regulate insensible...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2017-11, Vol.284 (1867), p.20171478-20171478
Main Authors: Eto, E. C., Withers, P. C., Cooper, C. E.
Format: Article
Language:English
Subjects:
Ambient temperature
Animals
Biological Evolution
Birds
Body Temperature
Conductance
Convergence
Development And Physiology
Endotherm
Environmental conditions
Environmental regulations
Evaporation
Evaporative Water Loss
Heat loss
Humidity
Mammals
Melopsittacus - physiology
Metabolic rate
Physiology
Pressure
Relative Humidity
Resistance
Thermal conductivity
Vapor pressure
Water loss
Water Loss, Insensible
Water vapor
Water Vapour Pressure
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Summary:Birds have many physiological characteristics that are convergent with mammals. In the light of recent evidence that mammals can maintain a constant insensible evaporative water loss (EWL) over a range of perturbing environmental conditions, we hypothesized that birds might also regulate insensible EWL, reflecting this convergence. We found that budgerigars (Melopsittacus undulatus) maintain EWL constant over a range of relative humidities at three ambient temperatures. EWL, expressed as a function of water vapour pressure deficit, differed from a physical model where the water vapour pressure deficit between the animal and the ambient air is the driver of evaporation, indicating physiological control of EWL. Regulating EWL avoids thermoregulatory impacts of varied evaporative heat loss; changes in relative humidity had no effect on body temperature, metabolic rate or thermal conductance. Our findings that a small bird can regulate EWL are evidence that this is a common feature of convergently endothermic birds and mammals, and may therefore be a fundamental characteristic of endothermy.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2017.1478