Penguin Billing Sound for the Socially Awkward (Sound of the Day)

We all know penguins as those well-dressed, black-and-white birds from the icy hinterlands. Did you know that these classy (and also endangered) birds often greet one another by tapping their bills against each other's—it's called 'billing'. As this sound effect also demonstrates, penguins sometimes greet one another with a grunt.