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Updated: Sep 7, 2025
Using a Thermal Camera to Measure Heat Loss Through Bird Feather Coats
Published on: June 17, 2020
Respirometry protocols for avian thermoregulation at high air temperatures: stepped and steady-state profiles yield
James C Short1,2, Marc T Freeman1,2, Andrew E McKechnie1,2
1South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, PO Box 754, Pretoria 0001, South Africa.
Abstract:
Relationships between air temperature (Tair) and avian body temperature (Tb), resting metabolic rate (RMR) and evaporative water loss (EWL) during acute heat exposure can be quantified through respirometry using several approaches. One involves birds exposed to a stepped series of progressively increasing Tair setpoints for short periods (<20-30 min), whereas a second seeks to achieve steady-state conditions by exposing birds to a single Tair for longer periods (>1-2 h). To compare these two approaches, we measured Tb, RMR and EWL over Tair=28°C to 44°C in the dark-capped bulbul (Pycnonotus tricolor). The two protocols yielded indistinguishable values of Tb, RMR and EWL and related variables at most Tair values, revealing that both are appropriate for quantifying avian thermal physiology during heat exposure over the range of Tair in the present study. The stepped protocol, however, has several ethical and practical advantages.
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