Birds clap in the dark to flirt: Nightjars reveal a hidden language of sound‎

Some birds sing to attract a mate. Others dance or display colorful feathers. But in the moonlit forests and shrublands of northern Argentina, one bird courts romance by snapping its wrists together, producing a sharp clapping sound scientists have puzzled over for decades. Now, researchers have captured the behavior in detail for the first time, revealing how scissor-tailed nightjars create one of the most curious sounds in the avian world.