Biologist surveying a track made by kakapo.

Breeding Kakapo have a very unusual mating system called a 'lek system'. In summer the males gather on traditional 'display grounds'- specially dug out hollows or bowls in the earth linked by well-formed tracks. The bowls are excavated and meticulously maintained by the male. He neatly clips the plants on the sides of the bowl, as well as along the tracks which are up to 50 meters long! The kakapo is the only 'lek' parrot, and the only lek bird to have evolved in the absence of predatory mammals.

At the lek sites, males vie for the best bowls. What happens next is arguably one of the most bizarre and amazing vocal displays of the bird world. Sitting in or near the bowls, the male kakapos start "booming". It is a sound that resembles distant thunder, or a deep resounding heartbeat. To produce the deep bass sound, the male kakapo inflates air sacs in his chest and belly. The booming calls start out softly, become louder and then slowly fade away. The calls can be heard from 1-5 kilometers away, depending on wind direction. The males boom an average of 1,000 times per hour, 6-7 hours per night! They do this every night for three to four months, to attract females. Once the female arrives at the bowl, the male will perform a type of dancing display and if all is well, mating will occur.

Kakapo mate only once every three or four years. They breed only in years when food is abundant, to insure plenty of nourishment for their chicks. Two or three eggs are laid on the ground, usually under a clump of tussock, in a hole in a bank or a rotten tree.

Eggs in a hollow tree bottom.

Kakapo chick with surrogate mother puppet.

Males play no part in rearing the young. Thus, while the females search for food the young are left unattended for long periods at night. There is a ten week nesting period, and after the first few weeks the female visits the nest only once or twice each night to feed the chicks. Young kakapo stay on the ground and are very loudly vocal day and night. This makes them quite vulnerable to predatory mammals, and eggs are easily preyed upon by rats.

Populations
There are now approximately 62 kakapo left in the world.