It’s shortly before dusk in the forests of New Zealand, and a kakapo is emerging from its burrow.
This flightless bird is vulnerable to aerial predators like falcons, so it only comes out as the sun starts to go down.
The kakapo is the heaviest species of parrot in the world and since it cannot fly, it climbs and skips.
That noise is a Kakapo mating call.
The male creates the deep sounds by puffing out the air sacs on his chest.
The serenade can last for up to eight hours, and can be heard from over four kilometres away.
But despite all his effort, even if a female does hear the mating call, she might ignore it.
Laying eggs requires a lot of energy, so mating will only take place if there is an abundant food supply.
This behaviour means that, despite living for up to 100 years, the kakapos are very slow to reproduce, only breeding every 2 to 5 years.
The kakapo evolved in the absence of terrestrial predators and was once New Zealand’s most common herbivore.
But over the centuries, rats and stoats were brought to New Zealand by settlers and the kakapo population plummeted.
By 1995, there were just 51 kakapo left.
In a bid to save the species from extinction, all remaining birds were evacuated to predator-free islands, and a captive breeding programme was started.
The kakapo is now on the road to recovery.
Kakapo population in 2012: 60 females, 64 males