Heaviest parrot

The world's heaviest species of parrot is the kākāpo (Strigops habroptilus), aka the owl parrot, nowadays confined in the wild to three tiny islets off the two major islands of New Zealand. Males are bigger than females, and weigh up to 4 kg (8 lb 13 oz) at maturity, due in part to this species' flightless nature, a unique feature among living parrot species. It's also able to build up considerable amounts of body fat for energy store purposes – another attribute unique to this species among parrots.

One of the world's rarest parrots, the kākāpo is categorized as Critically Endangered by the IUCN. It formerly existed on both North Island and South Island, but its flightless nature made it vulnerable to predation by human-introduced mammalian predators, such as dogs, cats and rats, rapidly leading to its extermination.

In August 2019, an extinct species of parrot, called Heracles inexpectatus, was described in Biology Letters that was twice the weight of the kākāpo and stood about 1 m (3 ft 3 in) tall, making it the largest parrot ever.