These birds clack their wing bones together to woo mates at night

A series of sharp cracks splits the nighttime air in a forest in the Andean foothills. But this isn’t the sound of boots snapping twigs underfoot. It’s a bird.

Male scissor-tailed nightjars (Hydropsalis torquata) create these abrupt sounds by hitting the bones in their wings together in a forceful snap, researchers report in the May Journal of Avian Biology.