Kakapos mate only once every three or four years. To attract a mate, the males make a loud "booming" noise. They do this every night for about three months. The female lays two or three eggs in a nest on the ground. She looks after the eggs herself. When the chicks hatch, she has to go and find food for them. This means she often leaves them alone and unprotected.
Kakapos were plentiful until the arrival of the Europeans in the early 19th century. The Europeans introduced cats, dogs and rats. The flightless kakapo and the unprotected kakapo chicks had little chance against these predators. By the 1970s the kakapo was extinct on the mainland. But thanks to the efforts of conservationists a few survive on offshore islands. The present population is estimated to be about 60.