These are thermal images of a female Southern Yellow-billed Hornbill (Tockus leucomelas) at different air temperatures.
Surface temperature (°C) is shown by the scale bar to the left of each image.
Top left: the hornbill at air temperature (Ta) = 15°C: beak surface temperature (Ts_beak) matches background Ts. Top right: the hornbill at threshold Ta = 30.7°C, Ts_beak is changing, lower mandible first. Bottom left: the hornbill at air temperature (Ta) = 32.2°C, note that Ts_beak is much higher than that of the rest of the body and the environment, indicative of heat being radiated from the beak. Bottom right: the hornbill at Ta >Tb (Ta = 43°C). The beak is cooler than the surrounding environment and the bird is using evaporative water loss to keep cool, as indicated by the open beak panting behavior.
All figures and photographic images will be published under a Creative Commons Attribution License (CCAL), which allows them to be freely used, distributed, and built upon as long as proper attribution is given.