The Kakapo (Strigops habroptilus), or night parrot, is a large, flightless, nocturnal parrot endemic to New Zealand. The Kakapo is certainly the world's rarest and strangest parrot being flightless, nocturnal, it emits a subsonic mating "boom" that can travel a few kilometres, as well as being the heaviest parrot in the world weighing up to 3.5kg. The arrival of Polynesian peoples, followed by Europeans in the 1800's, brought a wealth of pests and livestock with them resulting in the massive decline of Kakapo populations, from hundreds of thousands throughout the country to a mere handful of birds surviving on just two small offshore islands today. The Kakapo is critically endangered, however the population is increasing again with intensive conservation efforts ensuring their survival with a population of around 130 birds as of 2010.