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 nests are intensively managed. Before Polynesian rats were removed from Whenua Hou, they were a threat to the survival of young kakapo. Of 21 chicks that hatched between 1981 and 1994, nine were either killed by rats or died and were subsequently eaten by rats. Nest protection was intensified after 1995 by using traps and poison stations as soon as a nest was detected. A small video camera and infra-red light source would watch the nest continuously, and scare approaching rats with flashing lights and loud popping sounds. All kakapo islands are now rat-free, but infrared cameras still allow rangers