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Understanding energy metabolism in free-ranging animals is crucial for ecological studies. In birds, red blood cells (RBCs) offer a minimally invasive method to estimate metabolic rate (MR). In this study with European starlings Sturnus vulgaris, we examined how RBC oxygen consumption relates to oxygen use in key tissues (brain, liver, heart, and pectoral muscle) and versus the whole-organism measured at basal levels. The pectoral muscle accounted for 34-42% of organismal MR, while the heart and liver, despite their high mass-specific metabolic rate, each contributed 2.5-3.0% to organismal MR. Despite its low contribution to organismal MR (0.03-0.04%), RBC MR best predicted organismal MR (r=0.70). Oxygen consumption of the brain and pectoralis was also associated with whole-organism MR, unlike that of heart and liver. Overall, our findings demonstrate that the metabolism of a systemic tissue like blood is a superior proxy for organismal energy metabolism than other tissues.


Version posted is the In press pre-proof, available online October 23, 2023.

Open access under Creative Commons License Attribution-NonCommercial-NoDerivs 4.0 International



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Creative Commons License

Creative Commons Attribution-Share Alike 4.0 International License
This work is licensed under a Creative Commons Attribution-Share Alike 4.0 International License.



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