Non-evaporative heat dissipation across the beaks and casques of large forest hornbills.

Heat loss across the beak is an important thermoregulatory mechanism among birds, particularly in large-beaked taxa such as toucans (Ramphastidae) and hornbills (Bucerotidae). The number of species investigated remains limited, as does our understanding of how the functional significance of this pathway varies with environmental variables such as humidity, with little previous research on species inhabiting humid environments. We used infrared thermography to test the hypothesis that large (600-1300 g) Afrotropical forest hornbills use their beaks and casques as thermal radiators.