The Birdman ceremony took place annually at the September equinox, when the chiefs of the various kin-groups assembled at Orongo to compete. The aim was to find the first egg laid by the sooty tern (a migratory bird) on Motu Nui, the largest of three islets sitting opposite Orongo, 2km out to sea. Each chief would choose a representative, or hopu, who would scale down the sheer cliff to the ocean and swim through shark-infested waters to the islet. It could take several weeks for the egg to be found; meanwhile, the chiefs would remain in Orongo, where they participated in ritual dances, songs and prayers.
Once the egg was finally found, its discoverer would bellow the name of his master, and then swim back to the island with the egg tucked into a headband. The victorious chief now became the new tangata manu, or birdman. The new birdman would first have all the hair shaved off his head; he would then live in strict seclusion for a whole year in a sacred house at the foot of Rano Raraku, eating only certain foods, and forbidden to bathe or cut his nails. His kin-group, meanwhile, was endowed with a special, high status, which was often taken as an excuse for members to dominate and bully their rival groups.