Thermal Imbalance Drives Avian Performance and Responses to Climate Warming

Authors

• Cody K. Porter, Iowa State University
• David R. Adams, University of Central Arkansas
• Ofir Levy, Tel Aviv University
• Nathan Urinovsky, Tel Aviv University
• Eric A. Riddell, Iowa State University

Document Type

Article

Publication Date

10-20-2026

Publication Source

Proceedings of the National Academy of Sciences of the United States of America

Volume Number

123

Issue Number

42

ISSN

00278424

E-ISSN

10916490

Article Number

e2630333123

Abstract

Thermal performance curves are widely used to predict ectothermic responses to climate warming but are less effective for predicting endotherm performance across environmental conditions because thermoregulation often decouples body temperature from ambient temperature. We develop theory and provide empirical evidence for performance curves in endotherms structured by net sensible heat flux (Q), an integrative index of thermoregulatory imbalance. Using biophysical simulations in tree swallows, we show that performance varies predictably with Q (which we term “QPCs”), thereby explaining variation in nestling provisioning performance, reproductive fitness, and geographic limits, while also forecasting responses to climate change. We also demonstrate that thermal imbalance helps shape breeding ranges of birds across North America. Our findings introduce Q as a broadly relevant ecophysiological dimension that constrains performance in endotherms and provides a framework for predicting endotherm responses to climate warming.

Keywords

climate change, ecophysiology, thermoregulation, biophysical eclogy, tree swallow

Recommended Citation

Published in: Proceedings of the National Academy of Sciences of the United States of America, Volume 123, Issue 42, October 20, 2026.