Kakapo the reason for its massive decline since the introduction of dogs, cats and mustelids (see "Conservation: Human impact"). The kakapo is the only species of flightless parrot in the world, and the only flightless bird that has a lek breeding system. Males loosely gather in an arena and compete with each other to attract females. Females listen to the males as they display, or "lek". They choose a mate based on the quality of his display; they are not pursued by the males in any overt way. No pair bond is formed; males and females meet only to mate. During
Kakapo approximately every five years, with the ripening of the rimu fruit. In mating years, males making "booming" calls for 6–8 hours every night for more than four months. Each court consists of one or more saucer-shaped depressions or "bowls" dug in the ground by the male, up to deep and long enough to fit the half-metre length of the bird. The kakapo is one of only a handful of birds in the world which actually constructs its leks. Bowls are often created next to rock faces, banks, or tree trunks to help reflect sound: the bowls themselves function as amplifiers