Why the Kākāpō Parrot Makes Such a Haunting, Subsonic “Boom” Sound

If you’ve ever been out in the New Zealand wilderness, you might have heard a distinctive, low-frequency tone. It sounds less like an animal than the kick on an electronic drum machine. A look through the foliage to find the sound would inevitably put you face-to-face with the unlikeliest candidate: the kākāpō parrot.

Also known as the owl parrot or the owl-faced parrot, kākāpōs are a species of large, ground-dwelling parrot endemic to New Zealand. The only flightless parrot in the world, the Kākāpō is equally famous for its unique, almost subsonic boom. Let’s learn more about this fascinating bird and why it makes that strange “booming” sound.

Kākāpō Characteristics

In the natural world, the kākāpō wins out in many “only” categories. It’s the only flightless parrot (and heaviest), the only parrot with a polygynous lek breeding system, and quite possibly, one of the oldest living birds. Twenty-five inches long and characterized by owl-style front-facing eyes, yellow-green plumage, and short tails, kākāpōs typify bird evolution on oceanic islands.

It’s also nocturnal, roosting in the ground or under tree cover by day before venturing around its territory at night. Since kākāpōs can’t fly, they have very low metabolic demands. This means they can subsist on little food with even less nutritional value. Its diet includes seeds, fruits, leaves, and even rhizomes.

Without the ability to fly, kākāpōs make good targets for New Zealand’s birds of prey. Luckily, they adapted to their predators, growing camouflage-like feathers and keeping their activity to the nighttime. If a kākāpō is spotted by a predator, it freezes, effectively concealing itself in surrounding foliage. This helped them survive, at least until humans showed up. Due to invasive predators and overhunting for their prized feathers, kākāpōs have become critically endangered. Tragically, as of 2024, only 244 individuals remain.

However, the most interesting thing about this already fascinating animal is its eerie, electronic-like vocalizations. Let’s learn more about the kākāpō “boom,” which you can hear here.

The “Boom”

As you can see in this YouTube video, the kākāpō makes an arresting sound. While most parrots have a variety of calls, the male kākāpō makes a sound unique to New Zealand, if not the world of birds. To breed, male kākāpōs gather in an area. They fight each other, sometimes to the death, to secure the best courts. Once entrenched in their courts (dugouts in the ground next to trees or rocks) they compete for females by emitting the best “booms.”

These courts or bowls function like amplifiers for the male kākāpō booms. Once firmly in place, the males begin emitting these booming sounds by inflating the thoracic sacs in their chests. Starting with loud grunts, the males reach a subsonic pitch below 100 Hz of “booming.” After about twenty booms, the males emit a high-pitched, metallic sound, before starting the process over again. They do this for up to eight hours a night, often for three to four months in a row. In the process, male kākāpōs lose half their body weight. If they’re lucky, they attract a mate. If not, they attract a predator, since their booms reach over half a mile away.

Since kākāpōs only mate every five years (in tandem with the ripening of rimu fruit), this booming is integral to the continuation of their species. Kākāpōs aren’t the only birds to make a booming sound to attract mates (the Bittern heron also does), but they remain the most unique type of parrot on earth.