The answer is not as simple as saying, “because birds fly.” Birds such as penguins, emus and kiwis don’t fly at all despite having complex feathers. But most birds do fly, and their entire bodies, ...

This is a closeup of a back contour feather barb from a male eastern bluebird; demonstrates a protein with channel-type nanostructure. (Scale bar = 500 nanometers.) Image courtesy of Richard Prum Lab ...