|
|
|
|
Nestoridae
|
| |
|
| |
The parrot family Nestoridae consists of two genera, Nestor and Strigops. The genus Nestor consists of the Kea, Kaka, Norfolk Island Kaka and Chatham Island Kaka, while the genus Strigops contains the iconic Kakapo. All species are endemic to New Zealand and nearby oceanic islands like Chatham Island of New Zealand, and Norfolk Island and Phillip Island of Australia. The modern common species names, Kea, Kaka and Kakapo, are the same as the original Maori names.
The Norfolk Island Kaka and the Chatham Island Kaka have become extinct in recent times, and the Kakapo, Kea, and the two subspecies of the Kaka, are all threatened.
Discussion
Ask a question about 'Nestoridae' Start a new discussion about 'Nestoridae' Answer questions from other users |
Encyclopedia
The parrot family Nestoridae consists of two genera, Nestor and Strigops. The genus Nestor consists of the Kea, Kaka, Norfolk Island Kaka and Chatham Island Kaka, while the genus Strigops contains the iconic Kakapo. All species are endemic to New Zealand and nearby oceanic islands like Chatham Island of New Zealand, and Norfolk Island and Phillip Island of Australia. The modern common species names, Kea, Kaka and Kakapo, are the same as the original Maori names.
The Norfolk Island Kaka and the Chatham Island Kaka have become extinct in recent times, and the Kakapo, Kea, and the two subspecies of the Kaka, are all threatened. Human activity caused the two extinctions and the decline of the other three species. Settlers introduced invasive species, such as pigs and possums, which eat the eggs of ground nesting birds, and additional declines have been caused by hunting for food, killing as agricultural pests, habitat loss, and introduced wasps.
The family diverged from the other parrots around 82 million years ago when New Zealand broke off from Gondwana, while the ancestors of the genera Nestor and Strigops diverged from each other between 60 and 80 million years ago.
Systematics
No consensus existed regarding the taxonomy of Psittaciformes until recently. Consequently, the placement of the Nestoridae species has been variable. This family is one of three families in the order Psittaciformes; the other two families are Cacatuidae (Cockatoos) and Psittacidae (true parrots). The family is subdivided in two tribes, Nestorini and Strigopini, each with a single genus, Nestor and Strigops, respectively. Traditionally, the species of the family Nestoridae were placed in the family Psittacidae, but several studies confirmed the unique placement of this group at the base of the parrot tree. Most authors now recognize this group as its own family, while others argue that the two tribes in this family should be recognized as two separate families: Nestoridae and Strigopidae.
Phylogeography
The phylogeography of this group is rather well established and a nice example of various speciation mechanisms at work. Around 82 million years ago, ancestors of this group became isolated from the remaining parrots when New Zealand broke away from Gondwana, resulting in a physical separation of the two groups. This mechanism is called allopatric speciation. Over time, ancestors of the two surviving genera, Nestor and Strigops, adapted to different ecological niches. This led to reproductive isolation, and example of ecological speciation. In the Pliocene, around five million years ago, the formation of the Southern Alps diversified the landscape and provided new opportunities for speciation within the genus Nestor. Around three million years ago, two lineages adapted to high altitude and low altitude, respectively. The high altitude lineage gave rise to the modern Kea, while the low altitude lineage gave rise to the various Kaka species. Island species diverge rapidly from mainland species once a few vagrants arrive at a suitable island. Both the Norfolk Island Kaka as well as the Chatham Island Kaka are the result of migration of a limited number of individuals to islands and subsequent adaptation to the habitat of those islands. The lack of DNA material for the Chatham Island Kaka makes it difficult to establish precisely when those speciation events occurred. Finally, in recent times, the Kaka populations at the North Island and South Island became isolated from each other due to the rise in sea levels when the continental glaciers melted at the end of the Pleistocene.
Until modern times New Zealand and the surrounding Islands were not inhabited by four-legged mammals, an environment that enabled some birds to adapt to make nests on the ground and others to become flightless.
The parakeet species belonging to the genus Cyanoramphus (kakarikis) belong to the true parrot family Psittacidae and are closely related to the endemic genus Eunymphicus from New Caledonia. They reached New Zealand between 450,000 and 625,000 years ago from mainland Australia by way of New Caledonia.
Species
Nestorini
There are two surviving species and at least one well documented extinct species of the Nestorini tribe. Very little is known about the Chatham Island Kaka.
Strigopini
The Kakapo is the only member of the Strigopini tribe.
Common names
All common names for species in this family are the same as the traditional Maori names. The word ka (a is pronounced as long aa) means 'to screech', and duplicated, as Kaka, it becomes parrot. Kakapo is a logical extension of that name as po means night, resulting in Kaka of night or Night parrot, reflecting the species' nocturnal behaviour. The etymology of Kea in Maori is less clear, and might be onomatopoeic of its call kee-aah. In the anglicized versions of the names, the long versions of the vowels with diacritic marks , a and o, are replaced by a or o. In the Maori language, this changes the meaning of Kaka from parrot to dress or clothing.
Ecology
The isolated location of New Zealand has made it difficult for mammals to reach the island. This is reflected in the absence of land mammals other than bats. The main predators were birds: eagles (Eyles' Harrier, Kahu and Haast's Eagle ), falcons (Karearea) and owls (Whekau and Ruru). Many of the adaptations found in the avifauna reflect the unique context in which they evolved. This unique balance was disrupted with the arrival of the Polynesians, who introduced the Polynesian rat and the Kuri (Polynesian dog) to the island. Later, Europeans introduced many more species, including large herbivores and mammalian predators.
The three extant species of this family occupy rather different ecological niches, a result of the phylogeographical dynamics of this family. The Kakapo is a flightless, nocturnal species, well camouflaged to avoid the large diurnal birds of prey on the island, while the local owls are too small to prey on the Kakapo at night. The Kakapo is the only flightless bird in the world to use a lek-breeding system. Usually, they breed only every 3–5 years when certain podocarp trees like rimu (Dacrydium cupressinum) mast abundantly.
The Kea is well adapted to life at high altitudes, and they are regularly observed in the snow at ski resorts. As trees are absent in the alpine zone, they breed in hollows in the ground instead of in tree hollows like most parrot species.
Relationship with humans
Importance to the Maori
The parrots were important to the Maori in various ways. They hunted them for food, kept them as pets and used their feathers in weaving such items as their Kahu huruhuru (feather cloak). Feathers were also used to decorate the head of the taiaha, a Maori weapon, but were removed prior to battle. The skins of the Kakapo with the feathers attached where used to make cloaks (kakahu) and dress capes (kahu kakapo), especially for the wives and daughters of chiefs. Maori like to refer to the Kaka in the tauparapara, the incantation to begin their mihi (tribute), because their voice (reo) is continuous.
Status
Of the five species, the Norfolk Island Kaka and Chatham Island Kaka became extinct in recent history. The last known Norfolk Island Kaka died in captivity in London sometime after 1851, and only between seven and 20 skins survive. The Chatham Island Kaka went extinct between 1550 and 1700 in pre-European times, after Polynesians arrived at the island, and is only known from subfossil bones. Of the surviving species, the Kakapo is critically endangered, with only 90 living individuals. The mainland Kaka is listed as endangered, and the Kea is listed as vulnerable.
Threats
The fauna of Aotearoa (Maori for New Zealand) evolved for a long time in the absence of humans and other mammals. Only a few bat species and sea mammals were present prior to colonisation by humans, and the only predators were birds of prey that hunt by sight. These circumstances influenced the evolution of New Zealand's parrots, for example, the adaptations to flightlessness of the Kakapo and the ground breeding of the Kea. Polynesians arrived at Aotearoa between 800 and 1300 CE, and introduced the kuri (dog) to the islands. This was disastrous for the native fauna, because mammalian predators can locate prey by scent, and the native fauna had not evolved a defence against them.
The Kakapo was hunted for its meat, skin and plumage. When the first European settlers arrived, the Kakapo was already declining but still widespread. The large scale clearance of forests and bush destroyed its habitat while introduced predators like rats, cats, and stoats found the flightless ground-nesting birds easy prey.
The Kaka is a species that needs large tracts of forest to thrive, and the continued fragmentation of forests due to agriculture and logging has a devastating effect on this species. Another threat comes from competition with introduced species for food, for example with possums for the endemic mistletoe and rata and with wasps for shimmering honeydew, an excretion of scale insects. Females, young and eggs are particularly vulnerable in the tree hollows they nest in.
The Kea nests in holes in the ground, again making it vulnerable to introduced predators. Another major threat, resulting from development of the alpine zone, is their opportunistic reliance on human food sources as their natural food sources dwindle.
Conservation
Recovery programs for the Kakapo and the Kaka have been established, while the Kea is also closely monitored. The 90 living Kakapo are all in a breeding and conservation program. Each one has been individually named.
External links
|
| |
|
|
