Executive summary
The year has been an exciting one for all involved with the project as we have started to make a difference, echoing the title of the Department's Strategic Business Plan 'Restoring the Dawn Chorus'. An increase in bird numbers, particularly robins and kaka, is the most obvious evidence of the benefits of our pest control, through reduced pressure from introduced predators. A chorus of bellbirds now greets the visitor on arrival. The positive effects on plants through removing most possums from the block, and on insects through removing predators and competitors may be less obvious, but the signs are already there. We have also made significant progress with project advocacy, enjoying the support of the St Arnaud community, and of groups and individuals further afield.
Key results
Possum control - vegetation response
A reduction in possum numbers by an estimated 96.9% was achieved by a bait station operation using 1080. The reduction achieved over the full year after ongoing brodifacoum use was 84.6%. Such signifiant reductions are considered very likely to lead to measurable changes in palatable plant species. Analyses of vegetation surveys are currently being undertaken, but already there are signs that mistletoes are enjoying considerable growth and fuchsia seedlings have appeared in one vegetation plot.
Rodent control - vegetation and bird response
Rat numbers were very low in the forest at the start of the year and continued that way during our bait station poisoning operation.
Mouse numbers were also very low initially and reached a peak of 4% 'tracking tunnel activity index' during the year. Comparing this with a trapping index of 10% from Mt Misery in the winter indicates our control was keeping numbers down, for tracking tunnels are considered as sensitive an indicator as traps.
Research carried out on a sample of robins recorded a very high nesting success of 90% compared to previous South Island studies (eg. 13.3% at Kaikoura). This we would attribute to the success of our rat control among other factors. Quarterly five-minute bird counts are being used to monitor the response of other species.
Predator control - bird response
Seven stoats were caught in 2096 trap-nights of ring Fenn trapping around kaka nests (all at the one nest). A full network of traps was established at the end of the year.
One feral cat was caught in a short period of live trapping and little cat sign seen on the block.
A large number of hedgehogs have been caught in traps set for predators.
A Science & Research team carried out a study of kaka here recording all four nests on the block being successful rearing a total of nine young. This compares with only two young produced from 20 nesting attempts over an 11 year period at nearby Big Bush where Landcare Research studied birds from the 1980s but no significant predator control was carried out. No nesting female kaka were lost in our area compared to four out of seven during the Big Bush study. This suggests our predator control was very effective.
Wasp control - invertebrate response
The wasp control programme was the largest ever attempted in New Zealand. Wasp activity was reduced in c.300ha of the lower part of the block by 79% in a bait station operation using ‘Finitron’™. 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 analysis of these has started based on advice produced under contract by Landcare Research.
Deer control assessment
Three deer were shot in a brief operation to assess the effectiveness of ground hunting here.
Land snail monitoring
Sample plots have been established for a new population of Powelliphanta rossiana patrickensis located at and above tree-line. A high proportion of intact shells suggested this population to be doing well, particularly in areas of tall tussock.
Vegetation and plant monitoring
A sample of tagged and measured individual endangered plants (3 species of mistletoes and Pittosporum patulum)has been established to monitor their response to herbivore control. Vegetation plots (20mx 20m), foliar browse index lines and one deer exclosure have been set up for long-term monitoring of vegetation changes. Beech seed is sampled annually at three sites. Almost no seed fell in 1996/97 and a small quantity in 1997/98.
Toxin monitoring
Monitoring of lake water and trout has detected no toxins reaching the lake system.
Advocacy and education
Considerable effort has been put in to establishing a project profile and generating community support. Three public events have been held, a project launch by Sir David Attenborough, an Open Day and Barn Dance a year later, and a ministerial launch of the project’s wasp control and the Department’s Strategic Business Plan. A project logo and slogan have been developed with the help of the local primary school and a twice-yearly newsletter established. A Visitor Services Concept plan was contracted to establish a programme of track and interpretation material for visitors. Work was undertaken with Rotoiti Lodge Outdoor Education Centre to develop biology projects for 6-formers in the project area.
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:
- Mustelid trapping programme set up as part of a national trial of two trap cover designs and use of real or artificial eggs. Insufficient animals caught yet to determine most effective system and trial continuing, but both designs and egg types have caught stoats.
- Established the importance of providing access from ground to Philproof bait stations if they are to be used for mouse control.
- Demonstrated that a wasp control technique developed for small areas could be applied to a larger one.
- Refined an anaesthesia technique for live-trapping of mustelids.
- Assisted in first cross-fostering of kea in the wild.
- Conducted a trial of distance sampling as a bird counting methodology (using bellbirds).