Species of bird
 ;templatestyles src="Template:Taxobox/core/styles.css" / ;
The New Zealand falcon (, "kārewarewa", or "kāiaia"; Falco novaeseelandiae) is New Zealand's only falcon, and one of only four living native and two endemic birds of prey. 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 5000–15000 individuals remaining. Under the New Zealand Threat Classification System the falcon is stable at Threatened, with conservation research needed.
Taxonomy.
The New Zealand falcon was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's "Systema Naturae". He placed it with the falcons and eagles in the genus "Falco" and coined the binomial name "Falco novaeseelandiae". Gmelin based his description on the "New-Zealand falcon" that had been described and illustrated in 1781 by the English ornithologist John Latham. Latham had examined specimens both in the British Museum and in the Leverian Museum.
Ornithologists variously described the New Zealand falcon as an aberrant hobby or as allied to three South American species – "F. deiroleucus" (orange-breasted falcon), "F. rufigularis" (bat falcon), and "F. femoralis" (aplomado falcon); molecular phylogenetic studies show that it is most closely related to the aplomado falcon. Three forms are apparent from their significantly different sizes, with the larger ‘eastern falcon’ form in the eastern and central South Island, the smaller ‘bush falcon’ form in the central and south North Island, and an intermediary ‘southern falcon’ form in Fiordland, Stewart Island, and the Auckland Islands. The relationships between the distantly spaced populations of the southern form are uncertain. Although neutral genetic markers show a recent history of the two more distinct forms, the substantial size difference is likely to be driven by ecological adaptation as they occupy different habitats. Conservation management had already avoided mixing of the different populations. The forms are classified separately under the New Zealand Threat Classification System. The eastern falcon is Threatened, Nationally Vulnerable with a stable population. The southern falcon is Threatened, Nationally Endangered with less than 1000 estimated individuals. The bush falcon is Nationally Increasing.
Description.
The forms of the New Zealand falcon differ in size, colouration, and habitat. The eastern falcon is larger and paler, while the bush falcon is smaller and darker. The southern falcon sits between the other forms in colouration and size, but has a habitat more similar to the bush falcon. The eastern falcon on average has more white tail bars in their tail feathers than the other two forms. The bush falcon primarily lives in forests while the eastern falcon is present in open steppe habitats. The bush falcons have shorter wings with better manoeuvrability within forests.
Male New Zealand falcons are about two-thirds the size of female falcons. The eastern form of the New Zealand falcon has an average wingspan of 83 cm (33 inches) in females and 72 cm (28 inches) in males. Males of the eastern form range in weight from 300g to 350g (10.6oz-12.3oz), and the bush form ranges from 250g to 300g (8.8oz-10.6oz). Females of the eastern form weigh between 450g and 600g (15.9oz-21.2oz), and females of the bush form weigh between 400g to 500g (14.1oz-17.6oz). The southern falcon weight sits between the eastern and bush forms.
Adult falcons have black, barred rufous, or grey feathers on their crown, nape, and back. The tail is black with white bars that vary in number. The wing tips are rounded and feathers are black or grey with bars on the inside. There is a cream streak down the throat from the beak and the breast is cream, with vertical streaks of black or dark brown. The abdomen is cream with streaked rufous. The base of the beak, eyes, and legs are all yellow. The beak is black with a tomial tooth. The claws are black and the eyes are dark brown. The legs are a dull yellow, which become vibrant for males during the breeding season.
Juvenile New Zealand falcons have a darker colouration and faint tail bars. The breast is brown and the abdomen is cream with fine brown streaks. The soft parts that become yellow are instead olive green, sky blue, or dull grey in adolescent falcons under 9 months old. The full adult plumage is reached by 16 months.
Distribution and habitat.
The New Zealand falcon is only found in New Zealand.
The native habitat of the eastern falcons in the eastern and central South Island is open country and steppes, with nests on steep slopes or rock ledges. In native podocarp broadleaf forests of the North Island the bush falcon hunts at forest edges and nests in pre-existing tree structures such as epiphytes and tree cavities of mature trees, or on a sheltered ground area. The southern falcon is found in the Auckland Islands, Stewart Island, and Fiordland in forest habitats near oceans, with ecological similarities to the bush falcon rather than the closer eastern falcon.
The native habitats of the New Zealand falcon have been reduced through human development of land for the purposes of agriculture, vineyards, forestry, and housing, impacting nest sites and prey abundance. The habitat range of the falcon has increased to include human-modified landscapes such as pine plantations in the North island and farmlands in the South Island. Falcons have been recorded living in or near exotic pine plantation stands since the 1990s, nesting in stands that are unplanted or less than 5 years old. Regeneration of other plants in older stands prevents the falcon from nesting on the ground. Eastern falcons in the South Island were translocated to vineyards in Marlborough and have been breeding successfully since 2006 with the help of supplementary feeding, hunting vineyard pests, and predator-proof nest sites.
Ecology and behaviour.
The New Zealand falcon is a sedentary bird that spends most of its time within or close to its home range. The home range of a falcon varies, with calculations from 200 km² to 15 km², with dependence on food availability. Outside of the breeding season solitary or pairs of falcons will use permanent sheltered roosts. The falcon will use a temporary roost during the breeding season if their nest site is far away from their permanent roost.
The falcon is noted to sunbathe for up to 30 minutes in the morning with its darker back to the sun.
The New Zealand falcon is aggressive to non-prey animals. When confronting another falcon, a swamp harrier, or strong prey on the ground the falcon will push its weight back towards its fanned tail and open its wings slightly. Its eyes stay on the combatant and it keeps its feet free to attack. It will sometimes lie on its back and defend itself with its feet. When intruders such as swamp harriers and humans get too close to nests the falcon will make loud "kekking" noises alongside stooping at the head of the intruder. Aggression towards other New Zealand falcons is seen during the breeding season but subsides outside of it. Observations of captive falcons stooping rabbits and a cat were noted as playful or territorial rather than for hunting purposes. Falcons of all ages and sexes will play, initiated by turning their head upside down. They will chase, swoop and mock-attack each other, or if alone they will attack sticks, clumps of grass, or roots. Breeding pairs will often play together. Sometimes prey is caught several times before being killed, as play or practice.
The New Zealand falcon has a high-pitched "kek kek kek" call that is usually heard in territory defence, with the male’s call at a higher pitch than the female’s. Adults will also chitter to each other, particularly after copulation. The "kekking" call is 3–12 syllables, is used by both sexes all year, and travels over long distances. The chitter is 3–6 syllables and is used with other falcons. There is a ‘chup’ call which sounds like the first syllable of a chitter, which is often used during play. In serious situations with other predators the falcon will ‘squeal’. The squeal is sometimes used by captive falcons during handling.
Both endoparasites and exoparasites have been noted on the New Zealand falcon, but are not considered a major threat. Lice are common on fledglings but once the down is replaced by adult feathers their abundance decreases.
Food and feeding.
The New Zealand falcon has a wide range of prey it hunts, but is mostly made up of live introduced and native birds caught in the air. The composition of bird prey is largely based on species abundance with little selection. The most common avian prey includes introduced finch species, silvereyes, blackbirds, and the yellowhammer. The falcon is adept at capturing introduced birds, with their make up in the prey composition being slightly higher than their proportional abundance. There is also little preference shown for the size of the prey, with birds from the 7g (0.25 oz) grey warbler to the 1300g (45.9 oz) pheasants hunted successfully. The falcon evolved without the presence of mammalian prey, but now small mammals like hares, rabbits, stoats, and rats make up a small part of their diet. They also hunt skinks and hard-bodied insects like beetles, locusts, and dragonflies. As the prey composition is closely related to the local species abundance, studies on the diet of the three forms come with slightly different results. The eastern falcon is recorded with a higher proportion of mammalian prey than the bush falcon. In pine plantations the bush falcon hunts a higher proportion of introduced birds. The southern falcon hunts forest birds as well as seabirds when they come in at dusk, and one was recorded eating a 975g (34.4 oz) little blue penguin.
The New Zealand falcon has little competition for food as there are no native mammalian predators, and 2 other native birds of prey are nocturnal. They do compete with the swamp harrier, which searches for prey while flying. The competition reduces over winter when the swamp harrier relies more on carrion that the falcon doesn’t eat.
The New Zealand falcon has many hunting techniques used to catch their wide variety of live prey, including multiple aerial hunting techniques for catching avian prey in the air or on the ground. These techniques are often used in combination with one another. It often hunts around forest edges or rivers where there are breaks from cover. It can search for prey from a still perched position, from flying, or stalking on the ground. When still-hunting it will perch and preen in a seemingly inactive way, moving perch every 10 or so minutes until it detects prey. It has two aerial searching techniques. It can soar and prospect 50m to 200m (164 ft-656 ft) high, which often leads to a direct or stooping attack on high flying prey. The more effective search strategy is contour-hugging, a fast flight that follows the shape of the landscape and allows the falcon to sneak up on and attack agile birds. These techniques lead to quick tail-chases and attacks rather than stalking like other birds of prey due to the fast flying speed of the falcon. Stalking occurs on the ground, usually after noticing the prey from above or after chased prey escapes to the ground. When prey escapes into dense foliage cover a falcon will dive after it to flush out the prey with the impact, then resume the chase. It has flexible and resilient feathers which protect it from injury during this, unlike other raptors. The falcon also has excellent hearing and will find prey through listening, particularly with nests of bird chicks. The falcon is not willing to dive into water after prey.
When prey is found it is quickly attacked. The most common is a direct flying attack, often made at low elevations where the falcon is above the prey. It approaches with a loud fast flapping-flight, using foliage cover or a rapid approach to take the prey by surprise. This is the first attack used by young falcons and has a success rate of around 40%. It is efficient on slow prey, but if used alongside contour-hugging it can be successful on fast and agile prey. If the first attack on a bird doesn’t succeed a tail-chase will ensue for up to 15 minutes before catching the prey or giving up. The falcon will stay 2m to 4m (6.6 ft-13.1 ft) behind the bird, and