The New Zealand falcon (Māori: kārearea or kāiaia ; Falco novaeseelandiae ) is New Zealand's only falcon. Other common names for the bird are bush hawk and sparrow hawk. It is frequently mistaken for the larger and more common swamp harrier. It is the country's most threatened bird of prey, with only around 3000–5000 breeding pairs remaining.
With a wingspan between 63 cm (25 in) and 98 cm (39 in) and weight rarely exceeding 450 g (16 oz), the New Zealand falcon is slightly over half the size of the swamp harrier, which it usually attacks on sight. (Unlike the swamp harrier, the New Zealand falcon catches other birds in flight, and rarely eats carrion.) The male is about two-thirds the weight of the female.
The New Zealand falcon is mainly found in heavy bush and the steep high country in the South Island, and is rarely seen north of a line through the central area of the North Island. A small population also breeds on the Auckland Islands; the species is known from the Chatham Islands from fossil remains.
An aggressive bird that displays great violence when defending its territory, the New Zealand falcon has been reported to attack dogs, as well as people.
The New Zealand falcon nests in a scrape in grassy soil or humus in various locations: under a rock on a steep slope or on a rock ledge, among epiphytic plants on a tree branch, or under a log or branch on the ground, or on bare ground, making the two or three eggs that they lay vulnerable to predators such as stray cats, stoats, weasels, possums, and wild dogs.
A major ongoing threat to the birds is electrocution. Both a five-year radio tracking study of released birds in Marlborough and an observational study in Glenorchy have attributed nearly half of the bird deaths to electrocution on 11,000 volt distribution transformers and structures.
The Cardrona Valley in the South Island has a small population of kārearea. The five-year project that started in 2019 will focus on collecting data on the kārearea to gather knowledge of sightings, locate breeding pairs, locate and monitor nests, and gain insights on breeding population, habitat use, and territory size.