A very versatile and adaptable species compared with many other falcon species. The relatively short, deep rounded wings, and long tail make them exceptionally maneuverable. Combined with their relatively long legs and toes this allows them to weave through dense bush and catch small birds on the wing. They often hunt from a perch ¾ up a tree but also hunt along habitat edges or surprise prey by contour-flying close to the ground. Home-range size differs between habitats but is around 9 km2 in pine forest.
Males are approximately a third smaller than females. All ages have a dark eye and a distinct moustache or malar stripe running from the back of a strongly hooked bill vertically down the face. Adults have yellow legs, eye-ring and cere (fleshy skin just above the beak) are largely dark brown on the back. They have a streaked cream breast and a rufous under tail and thighs.
Recent fledglings and juveniles are more uniformly dark brown, lacking the defined cream streaks on the breast, and their legs, eye-ring and cere are blue-grey.
Voice: A loud ‘kek kek kek’ is commonly uttered in defence of a territory by both adults during the breeding season. The female’s call is deeper than the male’s more high pitched call. Adult females and juveniles will also ‘whine’ for food and a ‘chitter’ is often uttered during interactions between falcons.
Falcons live in a wide variety of habitats from the coast to above the tree line, including native podocarp and beech forest, tussock lands, roughly grazed hill country and pine forest. They may also be found in more intensively farmed areas where suitable bush remnants remain.
Juveniles can be observed almost anywhere in New Zealand during winter as they disperse from their natal territories. A pair that breeds in Zealandia/Karori Sanctuary has a foraging territory that includes much of the central city.
Mostly small to medium-sized birds, but occasionally takes prey much larger than itself such as black shags, poultry and pheasants. They will also take mammals such as rabbits and ¾ grown hares. Juveniles especially will feed on insects including cicadas, dragonflies and huhu beetles, especially during the period that they are learning to hunt for themselves. Prey is generally taken in proportion to its abundance.
Like all falcons, the New Zealand falcon does not build a nest. Rather, it makes a scrape on the ground, under a rocky outcrop or in an epiphyte in an emergent forest tree into which it lays its eggs.
They breed in spring and summer. A typical clutch consists of 2–4 eggs which take about 33 days to hatch. Incubation is generally shared.
Nestlings are fed by both parents but the male does most of the hunting with the female guarding close to the nest until the nestlings are close to fledging, which occurs between 31 and 45 days after hatching.
Threats to the New Zealand falcon are not well understood.
Although still widespread where suitable habitat exists, numbers have declined and predation by cats, mustelids, and hedgehogs is emerging as a problem for ground nesting falcons.
It is likely that stoats and other mustelids prey on eggs and nestlings in ground and tree nests, and rats may do the same.
New Zealand falcons are also threatened by electrocution on power poles containing transformers.
Despite their fully protected status, New Zealand falcons are still shot by people, particularly when falcons occasionally kill racing pigeons or chickens.
Recently a new threat to New Zealand falcons has emerged in the form of wind farms. High mortality rates have been reported for some birds of prey at several overseas wind farms due to collision with the rotating turbine blades. The construction of wind farms in New Zealand falcon habitat may expose it to similar risks.