The New Zealand kākā (Nestor meridionalis) is a large species of parrot of the family Strigopidae found in New Zealand's native forests across the three main Islands of New Zealand. The species is often known by the abbreviated name kākā, although it shares this name with the recently extinct Norfolk kākā and Chatham kākā. Two subspecies of New Zealand kākā are recognised. It is endangered and has disappeared from much of its former range, though the re-introduction of North Island kākā at Zealandia in Wellington has led to an increasing population of the birds across the city.
Taxonomy
The New Zealand kākā 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 parrots in the genus Psittacus and coined the binomial name Psittacus meridionalis. The specific epithet meridionalis is Latin meaning "southern". Gmelin based his description on the "Southern brown parrot" from New Zealand that had been described in 1781 by the English ornithologist John Latham in his book A General Synopsis of Birds. Latham had examined a preserved specimen in the Leverian Museum in London. The New Zealand kākā is now placed in the genus Nestor that was introduced in 1830 by René Lesson.
There are two subspecies: the North Island kākā (Nestor meridionalis septentrionalis) and the South Island kākā (N. m. meridionalis), although more recent research has ruled out allopatric subspeciation. The Māori language name kākā means "parrot", possibly related to kā, 'to screech'.
The genus Nestor contains four species, two of which are extinct: the New Zealand kākā (Nestor meridionalis), the kea (N. notabilis), the extinct Norfolk kākā (N. productus), and the extinct Chatham kākā (N. chathamensis). All four are thought to stem from a "proto-kākā", dwelling in the forests of New Zealand five million years ago. The closest living relative to the genus Nestor is the kākāpō or owl-parrot (Strigops habroptilus). Together, they form the parrot superfamily Strigopoidea, an ancient group that split off from all other Psittaciformes before their radiation.
The New Zealand kākā's closest living relative is the kea; the kea and the New Zealand kākā became separate species 1.72 million years ago due to ecological divergence. This likely occurred due to changes in the climate during the Pleistocene that drove the New Zealand kākā to specialise in more forested environments and the kea to specialise in alpine and other habitats. It is closely related to the kea, but has darker plumage and is more arboreal. The forehead and crown are greyish-white and the nape is greyish brown. The neck and abdomen are more reddish, while the wings are more brownish. Both sub-species have a strongly patterned brown/green/grey plumage with orange and scarlet flashes under the wings; colour variants that show red to yellow colouration especially on the breast are sometimes found.
thumb|North-island-kaka
thumb|South-island-kaka
The calls include a harsh ka-aa and a whistling u-wiia.
Kākā beak morphology also differs slightly from its closest relatives, the kea and kākāpō. The rhinotheca (upper part of the beak) of the kākā is narrower than the kākāpō and slightly longer. However, it is not as long and sharp as the rhinotheca seen in kea. Male culmen lengths tended to be, on average, 13.6% and 12.4% larger than female culmen lengths.
Distribution and habitat
The New Zealand kākā lives in lowland and mid-altitude native forest. They tend to inhabit mature native forests with a more complex canopy. The kākā was once widespread throughout most of New Zealand; however, due to habitat modification, predation and resource competition from introduced animals, its distribution has now significantly decreased. From their reintroduction in 2002, North Island kākā continue to recolonise Wellington and a 2015 report showed a significant increase in their numbers over the preceding 12 years.
South Island kākā
New Zealand kākā are still considered common and easy to find in certain large forested areas of the South Island. Kākā can be found in Rotoiti Nature Recovery Project, along the Milford Track and in the Eglinton Valley in Fiordland National Park. The South Island kākā, N. m. meridionalis, can be distinguished from the North Island kākā by slight differences in its plumage. The South Island kākā has more white plumage on the top of its head compared to the North Island kākā and has brighter green plumage, with the North Island kākā having more olive-brown plumage. The South Island males also tend to weigh approximately 100g more than the North Island males. Their behaviour in group environments shows their high cognition by demonstrating their complex interactions through social play and communication. They are highly active at dawn and dusk and can sometimes be heard calling loudly. Kākā usually can be seen in groups of 3-5 and often forage alone but can form large groups around food sources like flowering or fruiting trees.
Breeding
thumb|New Zealand kākā pairs mating
thumb|Eggs laid by a North Island kākā in a wooden nestbox at [[Zealandia (wildlife sanctuary)|Zealandia wildlife sanctuary, Wellington]]
The New Zealand kākā nests in cavities in hollow trees. These trees are often mataī, rimu, tōtara, miro, hīnau and sometimes dead trees. Occasionally, in a good fruiting year, a pair can double clutch, often utilising the same nest hole for the second clutch and extending breeding into winter. with two chicks fledging.
Breeding behaviour
The kākā is a monogamous species that tends to breed in pairs; however, extra-pair copulations, while not common, do occur in kākā. Kākā social play can be defined as two individuals interacting and responding to each other and exchanging information. Social play in kākā evolved early on in their evolutionary history. It likely evolved to help cognitive development and social bonding, with social play helping kākā develop problem-solving skills and learn social cues, which is important for kākā when in groups. It has a brush tongue with which it uses to feeds on nectar, and it uses its strong beak to dig out the grubs of the huhu beetle and to remove bark to feed on sap. They consume nectar from plant species such as kōwhai, flax, rātā, and pōhutukawa. Sap feeding behaviour appears to be an important resource for kākā in many regions across New Zealand and for all individuals in kākā populations. This specialised brush tongue seen in kākā helps kākā more efficiently consume sap, nectar and honeydew by allowing them to lap up these resources more easily. A significant part of the behaviour and diet of some populations of kākā is boring into trees to dig insect larvae out like huhu beetle and kanuka longhorn beetle (Ochrocydus huttoni) larvae. The species is also listed under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) meaning international export/import (including parts and derivatives) is regulated.
Predation
As cavity nesters with a long incubation period that requires the mother to stay on the nest for at least 90 days, New Zealand kākā are particularly vulnerable to predation. Stoats were the main cause of death of nesting adult females, nestlings and fledglings, but possums were also important predators of adult females, eggs and nestlings. There is strong evidence that predation of chicks and females has led to a serious age and sex imbalance, even amongst ostensibly healthy populations.
In parts of the country, the Department of Conservation and local conservation groups have attempted to control predators of New Zealand kākā through the use of traps, ground baiting and the aerial deployment of sodium fluoroacetate (1080). Where pest control has been carried out, there has been a significant recovery of New Zealand kākā populations. For example, in Pureora Forest Park 20 kākā were radio-tracked in an area to be treated with aerial 1080 in 2001. In nearby Waimanoa Forest, which was not to be treated with 1080, nine kākā were radio-tracked. In the area where 1080 was used, all 20 birds survived that season. Of the nine birds tagged in the untreated area, five were killed by predators that same season.
Competition
Research has shown that honeydew is very important for breeding New Zealand kākā, especially for those breeding in southern beech forests. The difficult nature of controlling wasps makes the future of the New Zealand kākā very uncertain.
Competition has also been observed over gouges in trees created by kākā to access tree sap. The kākā also has a personified parent named Tū Mātāika with a Māori proverb about the kākā describing the great number of descendants of Tū Mātāika. Many kākā visit residential gardens and reserves, and this in turn has led to more interactions with people. People have been feeding the birds unsuitable food such as nuts, various grains and cheese. There have also been instances of kākā nesting in the roofs of houses. This interaction in Wellington has caused minor damage to outdoor furniture, buildings and trees. Property damage also occurred in areas closer to kākā sanctuaries like Zealandia, creating negative attitudes and divided opinions on feeding wild kākā in residential areas, especially between neighbours who do and do not feed kākā. However, most people report positive attitudes to the reintroduction of kākā in Wellington.