Susanna N Tsueda

1 INTRODUCTION Heatwaves are intensifying (Fischer et al., 2021), and researchers are mobilizing to assess which organisms are likely to persist in the face of climate change (Moore & Schindler, 2022). As we seek to understand the mechanisms that enable persistence, organismal approaches are essential because they allow interpretation of the valence of heat effects.

Abstract 1. The ability to cope with heatwaves is likely to influence species success amidst climate change. However, relatively little is known about heat-coping mechanisms in endotherms, which are increasingly pushed to their thermoregulatory limits. We experimentally elevated nest temperatures by 4.5°C for 4 hours, focused on 12-day-old tree swallows (Tachycineta bicolor). 2.