ABS 2023
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Male Bachman’s sparrows with larger beaks persist in territorial defense during simulated intrusions
Rindy C Anderson1, William Abbott2. 1Florida Atlantic University, Davie, Florida, United States; 2The Nature Conservancy, Sacramento, California, United States

During elevated sublethal temperatures, animals are forced to make behavioral and physiological tradeoffs. Animals must direct resources to thermoregulation, which can result in strained time and energy budgets. Temperature increases can lead to decreased effectiveness of foraging and reproductive behaviors, which can have fitness costs. In hot and humid regions, evaporative cooling is inefficient, so birds must rely on other methods such as radiative cooling. In birds, radiative cooling occurs through thermal windows including the beak. Larger beaks are thought to be more effective thermal windows. We asked how beak size relates to territory defense behavior in a South Florida population of Bachman’s sparrow. Using simulated territorial intrusions during peak heat and humidity, we asked if differences in beak size predicted differences in territorial defense. Birds with the largest beaks relative to their body size responded with more flights and songs and persisted in these behaviors longer than birds with smaller beaks. Understanding how organisms are affected by a hot and humid climate is paramount to understanding how they will respond to challenging climate patterns.