The Return of the kaka

Forest and Bird, Issue 296, 1 May 2000, Page 18

The Return of the kaka

KATHY OMBLER

reports on the war against wasps;

possums; rodents and stoats; in Nelson Lakes National Park:

he raucous screechings of a busy flock of kaka are a memorable welcome to the shores of Lake Rotoiti near St Arnaud, in Nelson Lakes National Park. According to the rather proud locals, these are the ‘teenagers’ of a growing lakeside population of this threatened native bush parrot. Their loud and youthful posturings become part of an astonishing symphony when the bellbirds and tui join in the daily dawn chorus. The cacophony of birdsong heralds the successes of a major conservation trial in the area. The Rotoiti Nature Recovery Project is a Department of Conservation initiative aimed to create a largely pest-free refuge in the honeydew beech forests beside Lake Rotoiti. The current area encompasses 825 hectares at Kerr Bay, close to St Arnaud village. Within three years the project team has achieved significant results by tackling both insect and animal pests. The possibility of extending the targeted area further along the lakeshore, and even into the Travers A popular walking track through the beech forest skirts the shores of Lake Rotoiti in the ‘mainland island’ area of Nelson Lakes National Park. Encouraging visitors to understand the effect of pest control particularly on birdlife is part of the project. Once visitors here were harassed at times by European wasps, 1.7 million of which have been exterminated. The sound of birdsong during the day is another sign of improved forest health.

Valley at the head of the lake, is currently under review. Nearby, some private landowners are initiating their own pest control programmes, based on the department’s methods. ‘We aim to develop pest-control techniques that can be applied more widely, says Dr David Butler, the project co-ordi-nator. ‘We also see the project as a catalyst, to show other organisations what can be achieved and encourage them to try it on the land they administer: The project was set up as a pilot for recovering the natural environment within large honeydew beech forests, which are extensive in the South Island. There are two major challenges: wasps and animal pests. Millions of European wasps invade these beech forests to feed on honeydew, which is produced on the trunks of beech trees by a tiny scale insect. The nectar is needed by native birds and insects but the wasps get to it first. The other problem is the consequence of the ‘beechmast cycle’. In seasons when the beech trees seed prolifically there is a population explosion of rodents. Then stoats, too, breed prolifically, turning on native birds when they have finished eating the mice and rats. Yellowhead, kaka and parakeets are particularly vulnerable to such pests because they nest in tree holes. The Rotoiti Nature Recovery Project is one of several forest-ecosystem recovery projects, or ‘mainland islands, managed by. the Department of Conservation. These

aim to restore and protect habitats on the mainland through intensive management of introduced pests. The Rotoiti project has concentrated on more than outright pest control, however. Results have been intensively monitored so that control methods can be fine-tuned. DoC has placed a strong focus on advocacy and education at the easily-accessed site. Community involvement is actively encouraged. "he three-year war on pests at Rotoiti has already reduced possum num- = bers by 97 percent. Decreased possum browsing in successive growing seasons has given their favoured vegetation a welcome break, with noticeable growth in endangered mistletoes and the rare Pittosporum patulum. In 1999, the biggest wasp-control operation ever attempted in New Zealand reduced wasps by 90 percent. This included the destruction of 2300 nests and 1.7 million wasps. Monitoring has confirmed that lower wasp numbers have increased honeydew supplies for native birds, and reduced wasp predation on invertebrates. A stoat-control programme, supported by local residents maintaining their own traps, is credited for the most successful

breeding season on record for kaka. In two years, four pairs of kaka nesting in the project area produced 12 surviving young. This season three nests contained 10 more chicks. All three have been closely watched by project staff. At the time of writing, three chicks in one of the nests had fledged, putting them beyond danger of stoat predation.

This summer season was especially challenging, requiring extra vigilance, reports David Butler. "The beechmast year meant more stoats. We caught as many in January as we did in the whole of last year. The fact that the kaka chicks have subsequently fledged means our trapping operation must be working’ Similarly, rat control has led to greatly increased productivity from resident robins. ‘We have established a clear linkage, he says. "Iwo seasons of intensive study have been enough to assure us that if we get rats down to a certain level, the robins will thrive’ This year 96 percent of robin nests studied were successful, while studies elswhere show only a 25 percent success rate. For two years, Lake Rotoiti schoolchildren have helped DoC with its robin monitoring.

here are currently eight staff working on the Rotoiti forest recovery team. David Butler says there are three reasons for the major staff input; the needs for intensive pest control, advocacy and monitoring. ‘There is a huge effort currently going into pest control, particularly on wasps, which is still very much in the experimental stage — we are trying slightly different things each year. ‘The significant beech-seeding last autumn presented us with large numbers of rodents and stoats too, which meant we could not reduce efforts in those areas. At the end of this season, we should know much more about our ability to manage beech forests through this dramatic cycle. ‘As the project profile increases and we have more results to show, we are doing a large amount of advocacy. We have been meeting an increased demand for talks and guided walks.’ As part of the strong advocacy focus, two new tracks, including one suitable for wheelchairs, have been constructed in the recovery area. The tracks are enhanced by several stylish, informative signs. ‘The Rotoiti project is ideally placed for people to see conservation work being undertaken, and to experience native forest that is alive with the sight and sounds of birds, says David Butler. There is a huge time component involved in the monitoring work. ‘This is particularly important, when we are trying to measure the results of modifying control techniques on different pests, says David Butler. "We also need to

know the results of our pest control on the native flora and fauna. For example: do we need to reduce pest numbers even further, or can we afford to reduce the effort?’ Monitoring methods and results are interesting, to say the least. Mice numbers are counted by tracking their footprints in 100 specially built tunnels, set up with paper, ink pads and peanut butter bait! One feral cat, fitted with a transmitter, travelled two complete circuits around Lake Rotoiti in three months. The Rotoiti project is now embarking on a review, looking at options ranging from scaling down the operation (in particular the monitoring work), to increasing the effort. ‘One scenario to consider is extending the project further along the lake towards or into the Travers Valley. Our ability to do this depends on research being carried out both here and at other sites in New Zealand, says David Butler. ‘For example the Hurunui "mainland island" project is testing the use of one line of possum-bait stations along a valley floor, for control of possums throughout a complete catchment. The Northern Te Urewera team is looking at different methods of applying rat control over large areas, including trapping. ‘We are assisting Landcare Research with trials to develop an aerial bait for wasps and we are also testing how far we can stretch our current ground-baiting system. The further apart we can place our stations, the more area we can cover for the same effort. We are testing a system of stoat traps lined along natural features rather than a grid, and hoping to identify how to maximise captures for minimum effort by where we place traps. ‘If we could extend the project in a way that would reduce our boundary-to-area ratio, pest control could be more efficient. We could then consider reintroductions of some species with increased likelihood of success. ‘For example, kiwi researchers suggest that a "protected area" of about 4000 hectares may be needed to manage a sustainable kiwi population. This allows room enough for kiwi chicks to disperse, but still settle within a protected area.

KATHY OMBLER writes about nature and the outdoors from her home base in Wellington.