Scientists finally know why hummingbirds hum

Of all the birds on this planet, hummingbirds are one of the most unique and, dare I say, charming. Even if you live in an area with hummingbirds, actually seeing one can still be an extremely rare sight. You can boost your chances by putting out hummingbird feeders, which are basically fake flowers filled with a sugary mixture, but that's no guarantee of actually seeing one. When one swoops in, however, you'll definitely know it thanks to the bold humming sound it produces as its wings flap so ...