Relative to its body size, the huge beak of the toco toucan is the largest of any bird. It allows the toucan to eat both fruit and small animals, and display to both mates and rivals. Darwin himself speculated that it acts as a billboard, shaped by sexual selection to display bright colours that could be attractive to potential mates. But the toucan's bill has another function that has only been discovered. Like the ears of an elephant, the toucan's bill is a radiator.
It certainly has all the characteristics of a biological radiator. It's big and has a surface area that's 25-40 times…
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