1. The toco toucan possesses the largest beak relative to body size of all birds. The large surface area of their beaks may be an important mechanism for radiating heat (and thereby cooling the bird) as outdoor temperature increases. Shown in the graph are data for beak heat loss as a percent of total body heat loss, at various temperatures in degrees Celsius. 70 60 50 40 PERCENT HEAT LOSS FROM BEAK 30 20 10 5 10 15 20 25 30 35 TEMPERATURE (OC)