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 affectionate pet by the Māori. This was corroborated by European settlers in New Zealand in the 19th century, among them George Edward Grey, who once wrote in a letter to an associate that his pet kakapo's behaviour towards him and his friends was "more like that of a dog than a bird". The conservation of the kakapo has made the species well known. Many books and documentaries detailing the plight of the kakapo have been produced in recent years, one of the earliest being "Two in the Bush", made by Gerald Durrell for the BBC in 1962. A feature-length documentary,