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
Flightless cormorant A large oil spill would pose a threat. However, although the flightless cormorant population is small and its range limited, the ability of the species to breed quickly can allow it to recover from disasters as long as the population remains above a critical level. The flightless cormorant is one of the world's rarest birds. A survey carried out by the Charles Darwin Research Station in 2004 indicated that the species has a population of about 1,500 individuals. In 2009, BirdLife International set the number of individuals of the flightless cormorant at only 900 individuals, although a more recent estimate