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 of the birds had died and the fifth died after about four years. In the next 12 years, regular expeditions found few signs of the kakapo, indicating that numbers were continuing to decline. Only one bird was captured in 1967; it died the following year. By the early 1970s, it was uncertain whether the kakapo was still an extant species. At the end of 1974, scientists located several more male kakapo and made the first scientific observations of kakapo booming. These observations led Don Merton to speculate for the first time that the kakapo had a lek breeding system. From