Ornithologists variously described the New Zealand falcon as an aberrant hobby or as allied to three South American species ; however molecular phylogenetic studies show that it is most closely related to the South American Aplomado falcon Two forms are apparent from their significantly different sizes with the larger race in the South Island and the smaller in the North Island. Although neutral genetic markers show a recent history of these two forms, the substantial size difference is likely to be driven by ecological adaptation. Conservation management had already avoided mixing of the North Island and South Island populations.
Description
With a wingspan between and and weight rarely exceeding, the New Zealand falcon is slightly over half the size of the swamp harrier, which it usually attacks on sight. The male is about two-thirds the weight of the female.
Distribution and habitat
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.
Behaviour
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.
Breeding
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.
Relationship with humans
Although protected since 1970, the kārearea is a threatened species, with fewer than 8000 birds remaining. They continue to be persecuted by farmers and pigeon-owners: up to three-quarters of falcons die in their first year, mostly as a result of human actions.
Falcons for Grapes programme
In 2005, funding was given by the Ministry of Agriculture and Forestry towards a programme that uses the falcons to control birds that damage grapes and act as pests in vineyards as well as monitoring the birds and establishing a breeding population in the vicinity of the Marlborough wine region. Initially, four falcons were relocated to the vineyards from the surrounding hills. After the release of a further 15 birds breeding began to occur – the first time it is thought to have happened since land clearance 150 years ago.
Electrocution Threat
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.
Cultural references
The New Zealand falcon features on the reverse of the New Zealand $20 note and has twice been used on New Zealand stamps. It was also featured on a collectable $5 coin in 2006. The Royal New Zealand Air Force's aerobatic team is called the Black Falcons. The proverb "Me te kopae kārearea" or "like the nest of kārearea" means 'rarely seen.'
