What are the most elaborate animal courtship displays in nature?

The answer

The bowerbird of Australia and New Guinea builds elaborate decorated structures - not nests, but stages - using colored objects, flowers, and even stolen human items, arranged with forced perspective to make the male appear larger. Greater sage-grouse inflate twin yellow air sacs on their chests, producing booming sounds audible two miles away, while fanning tail feathers in precise sequences. Male peacock spiders perform choreographed dances, raising vibrantly colored abdominal flaps while vibrating at species-specific frequencies; one wrong move means being eaten by the female. The elaborate riflebird of paradise performs a spread-wing display that creates a velvety black optical illusion, using superblack feathers that absorb 99.95% of light.