Creating a Kaka sanctuary
Protecting a threatened species
Protection for the Kaka on the mainland of Aotearoa New Zealand is essential to their survival.
Our forest parrot, Nestor meridionalis, requires mainland sanctuaries that are surrounded by a well-designed and maintained predator proof fence or with a volunteer army of people doing efficient mammalian pest control, and preferably both.
Stoats, rats, possums and cats are the big four pests, and Kaka are most vulnerable at nesting when these pests kill Kaka eggs, chicks and adult females caring for the nest.
Kaka are hole-nesters, choosing to modify natural crevices in the trucks of large, mature native podocarp trees and create a nest inside the trunk with a narrow hole and large nest hollow. Despite that choice, access into the nest is no match for agile rats and stoats, and the young Kaka are easily predated.
Pre-human Kaka populations
Before humans populated this country, Kaka were as widespread as the mature lowland, podocarp forest that covered much of the land. Native food sources were plentiful for Kaka with few threats to successful nesting.
As man cleared forest from the landscape and changed the ecological balance in the early 19th century, the Kaka’s world shrunk. The introduction of pest predators slowly but steadily increased the pressure on the Kaka’s environment.
Native kiore rats are mainly fruit and seedeaters, but ship rats and browns rats that were stowaways to Aotearoa on the ships of whalers and early settlers, were and still are, a deadly threat to birdlife.
After the rats, came the stoats and ferrets introduced by the early Acclimatisation Society — stoats that are deadly and agile predators that feed on not just the eggs and chicks of tree nesting birds, but also on adult female birds tending a nest.
Kaka on the mainland, (except those in predator proof sanctuaries now), are always at risk of predation.
Stoats rats possums and cats
Not just from stoats and rats, but also possums (whose foraging can kill off nest trees such as Puriri), and cats that are particularly intrigued by the playful antics of juvenile Kaka learning to fly. Young Kaka spend around two weeks lower to the ground when they are particularly vulnerable.
Pest-free offshore islands in the upper half of the North Island have provided a natural sanctuary to a core population of Kaka, (such as on Hauturu Little Barrier and Aotea Great Barrier islands), and other islands in Northland and the Bay of Plenty. Further south, Kapiti Island is a sanctuary to Kaka off that coastline.
Mainland predator proof sanctuaries combined with intensive pest control in other areas around the country have helped to conserve a declining population of less than 10,000 Kaka. These endemic forest parrots are categorized as “nationally threatened” on the IUCN Red List of endangered species.
Despite bird sanctuaries and intensive pest control in forest areas from Northland to Stewart Island, the Kaka population continues a steady decline.
To fence or not to fence
Predator proof fencing costs around $100/metre depending on the lie of the land, so if your chosen sanctuary requires 5km of fencing, that’s half a million of capital up front, just for the fence. Construction and maintenance require even more resources.
The fence design needs to repel something as small as a mouse, as wily as a rat, as strong as a possum and as agile as a cat. The usual design incorporates a two-metre tall mesh covered fence with a buried mesh skirt and a large solid overlapping cap. An electrified wire is also a useful deterrent integrated into some designs.
A fenced sanctuary requires up front capital, ongoing maintenance and a strong funding organisation. The alternative of intensive mammalian pest control doesn’t require the same level of capital investment, but does also require fudning, strong organisation and committed volunteers.
Once the problem of controlling predator pests is decided, (and most sanctuaries provide protection for a number of endangered endemic bird species), there is still much that can be done.
Positive impact of removing predators
A habitat that is protected from pests will usually thrive with enhanced ecology and become a naturally attractive area to birds. The absence of possums is an example of a positive that will allow previously hard hit vegetation to bounce back and provide renewed habitat and food sources for our birds.
For example, not long after Tawharanui Regional Park (east coast north of Auckland) was protected with a predator proof fence, it was naturally populated with an influx of Bellbirds from Hauturu Little Barrier island, from 20km away across the Hauraki Gulf (near Auckland). Removing predators can allow better seed dispersal and vegetation regeneration that improves the local ecology for invertebrates as well as birdlife.
In autumn and winter, Kaka are regularly reported around the Auckland region, from the northeast coast around Leigh and Matakana, across the isthmus to Muriwai and the Waitakere Ranges Regional Park, as well as in south Auckland, the Hunua Ranges and the Franklin district.
Kaka continue to thrive
Several sanctuaries have had very successful breeding programmes using nest boxes and supplementary feeding stations, such as at Karori Sanctuary in central Wellington, where Zealandia has enabled the breeding of more than 250 young Kaka over the past decade.
Those Kaka have spilled over into the suburban and hill areas of Wellington City and also helped populate new areas in the region.
Besides the offshore islands where many Kaka return to breed in safety, away from pest predators, some of the other sanctuary areas that now see good numbers of Kaka are the large fully fenced Maungatautari Ecosanctuary in the Waikato region, and the open sanctuary on Mt Bruce in the Wairarapa.
Small natural populations of Kaka also exist throughout the country, such as in the forests of Pureora, Pirongia, and Kaimai Mamaku in the North Island, and in the South Island; in Able Tasman, Kahurangi, and the Fiordland forests.
In Southland, there are also good numbers of South Island Kaka in areas of Waitutu forest, Stewart Island and Whenua Hou/Codfish Island.
ENDS
