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Measuring power input, power output and energy conversion efficiency in un-instrumented flying birds
Linus Hedh1, Christopher G Guglielmo2, L Christoffer Johansson3
1Department of Biology, Lund University, 223 62 Lund, Sweden Anders.Hedenstrom@biol.lu.se Linus.Hedh@biol.lu.se.
The Journal of Experimental Biology
|August 16, 2020
Summary
This study introduces new methods to measure bird flight power, finding efficiency estimates close to the assumed 23% but with significant variation. These techniques enable better understanding of avian flight energetics.
Area of Science:
- Avian biology
- Bioenergetics
- Biomechanics
Background:
- Metabolic power (Pmet) estimation in birds relies on aerodynamic models and a constant efficiency factor.
- Previous assumptions of a 23% constant flight efficiency lack robust empirical support due to methodological limitations.
Purpose of the Study:
- To evaluate novel techniques for measuring mechanical power (Pmech) and metabolic power (Pmet) across various flight speeds in birds.
- To estimate flight efficiency in blackcaps using advanced measurement methods.
Main Methods:
- Utilized the 13C-labelled sodium bicarbonate (NaBi) method to measure Pmet.
- Employed particle image velocimetry (PIV) to measure Pmech in blackcaps during wind tunnel flight.
- Cross-validated NaBi measurements with quantitative magnetic resonance (QMR) in yellow-rumped warblers.
Main Results:
- NaBi-estimated Pmet was approximately 12% lower than QMR-estimated values.
- Pmet showed a U-shaped trend with flight speed, though not statistically significant.
- Estimated flight efficiency ranged from 14% to 22%, close to the commonly used 23% default.
Conclusions:
- The NaBi and PIV methods are validated as viable tools for studying bird flight energetics.
- These techniques can address key questions regarding the relationship between power, speed, and efficiency in avian flight.
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