Executive summary
Significant progress is recorded towards achieving two of the project’s three objectives, namely pest control/species recovery and advocacy. Initial discussions have begun regarding the third objective that covers re-introducing species lost from the area.
Key results
Possum control – vegetation response
Possums were maintained at low numbers below the target level throughout this period. Positive responses from the vegetation are becoming evident in the rare plants we monitor, mistletoes and Pittosporum patulum, and in the foliage condition of other palatable species.
Rodent control – bird response
Rodent numbers remained low and below target levels through to July 2000. Unusually heavy seeding of beech trees that autumn, following significant seeding the previous year, saw rats rise to unprecedented levels in non-treatment areas and to above our target in the treatment area. The low rat numbers in 1998/99 and 1999/00 were associated with very successful breeding seasons for robins. In 2000/01, though rat numbers went above our target, we were still able to exert sufficient control to see robins do significantly better than in the non-treatment area.
Rat control switched from using brodifacoum in 1998-2000 to traps in 2000/01, following a departmental review of the use of the toxin. Whether the change of technique was also a factor in the increase of rat numbers can only be determined in the future.
We were not able to control mice effectively with our current spacing of bait stations/traps.
Mustelid control – bird response
Our stoat trapping programme, combined with a likely secondary poisoning impact on this predator in 1998-2000, resulted in significantly higher nesting success of kaka in the project area (80% of nests successful) than elsewhere (5-10% success).
The combination of rat and mustelid control was associated with significant increases in a variety of native bird species. Bellbirds, rifleman and parakeets showed the strongest effects, the average number of the former doubling from two to four per count. All nine falcon eggs laid in the block (3 nests - 1999-2001) led to fledged chicks compared to only 27% of those at other sites in the area.
Wasp control – invertebrate response
Wasp activity was reduced in c300ha of the lower part of the block each year by a bait station operation. Over 90% of nests there were considered killed in 1998/99 and 2000/01 and a lower proportion in 1999/2000. A significant response was recorded in the output of honeydew by the beech scale insect, an important food source for native fauna. Honeydew remained above target levels in the treated area and fell below that due to wasps in the non-treatment area. Malaise trap samples have been collected to examine the impacts on other invertebrates and there are early signs of the expected positive effects.
Land snail monitoring
Our initial monitoring of the Powelliphanta population has been completed and suggests that it is relatively healthy in the one smallish area of tussock. It will be several years before a re-monitor is due to look for positive changes there and in the forest nearby.
Advocacy and education
Our advocacy and education programmes have developed significantly. A major effort was put into increasing what the site can offer to visitors. Two short walks, the Bellbird Walk and Honeydew Walk have been constructed to the Department’s highest standard, leading into the project area from Kerr Bay at Lake Rotoiti. The Bellbird Walk provides a 10-minute loop suitable for wheelchairs and the Honeydew Walk a 30-45 minute loop with a wide gravel surface. Interpretation panels have been positioned on these tracks and a new display area developed in the Visitor Centre. A major Open Day was held in 2000 and an increasing number of varieties of groups were given guided walks or talks about the project.
Educational resources were developed at primary and secondary levels and the project participated in the LEARNZ programme in 2001 when several thousand pupils from schools all around the country participated in ‘virtual field trips’ to the site.
Experimental work
It has been identified that Mainland Islands like Rotoiti should be sites where techniques are developed, tested or refined for application at other sites. It is thus appropriate to emphasise activities of this type as follows:
- A trial of two designs of trap cover for trapping of mustelids and of fresh and plastic eggs as bait led to clear preferences (wooden tunnel/fresh white egg) which were adopted throughout our trap network.
- Research to investigate optimum bait station spacing for control of rodents in beech mast years suggested that a 20x20m grid would be needed for effective control of mice.
The project continued to foster significant student research here. Its own studies provided further information on possum and mouse diets.
Spreading the message
We also emphasise the idea that mainland islands can act as catalysts, encouraging others to apply similar techniques on land they manage. Such information transfer is a weekly event by phone or e-mail though some specific activities can be identified:
- Provision of advice to local landowner seeking to tie pest control into a QEII covenant over forest on his property.
- Visit to the project by Jan and Arnold Heine of MIRO, a group proposing a community-based mainland island in Wellington’s East Coast Bays. Followed by an invitation to talk at the AGM of East Harbour Association in July 1999.
- Invitation received to participate in a workshop to discuss the formation of a community-based mainland island in the Waitakere Ranges of Auckland (August 1999).
- Organising of a Mainland Island hui in 2000 – one result was that the Bushy Park Homestead and Forest Trust turned around three quarters of its restoration programme (Allan Anderson, pers. comm.).
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