Data for: Adaptive variation in the upper limits of avian body temperature

Physiological performance declines precipitously at high body temperature (Tb), but little attention has been paid to adaptive variation in upper Tb limits among endotherms. We hypothesized that avian maximum tolerable body temperature (Tbmax) has evolved in response to climate, with higher Tbmax in species exposed to high environmental heat loads or humidity-related constraints on evaporative heat dissipation. To test this hypothesis, we compared Tbmax and related variables among 53 bird species at multiple sites in South Africa with differing maximum air temperatures (Tair) and humidity using a phylogenetically-informed comparative framework. Birds in humid, lowland habitats had comparatively high Tbmax (mean ± SD = 45.60 ± 0.58°C) and low normothermic Tb (Tbnorm), with a significantly greater capacity for hyperthermia (Tbmax -Tbnorm gradient = 5.84 ± 0.77 °C) compared to birds occupying cool montane (4.97 ± 0.99 °C) or hot arid (4.11 ± 0.84 °C) climates. Unexpectedly, Tbmax was signi...