Native birds soar - thanks to 1080
Native bird numbers are starting to bounce back in the Tararua range, thanks to aerial 1080 drops.
A 22,000-hectare zone of bush between Mt Holdsworth and Otaki Forks was selected for the eradication programme known as Project Kaka because of its diverse habitats, its popularity with tourists and because it is a natural corridor linking Kapiti Island and north Wairarapa's Pukaha Mt Bruce Wildlife Centre.
Co-ordinated by the Conservation Department and the Animal Health Board (AHB), the project aims to revive forest health and pump up native bird populations, while shielding Wairarapa cattle and deer herds from possum-spread bovine tuberculosis.
Monitoring by DOC, AHB, Landcare Research and Greater Wellington regional council has shown a marked drop in the number of possums, mustelids (stoats, weasels, and ferrets), rats, mice, deer, pigs, cats and dogs, as well as a jump in populations of some native bird species.
selected for its diverse habitats, its popularity with tourists and because it is a natural corridor linking Kapiti Island and north Wairarapa's Pukaha Mt Bruce Wildlife Centre.
James Griffiths of DOC has been analysing data from 360 bird-count sites, which are tallied twice during spring, across the 1080 drop zone.
The ledger shows rifleman, whitehead and kakariki - a species Forest & Bird says is in immediate danger of extinction - have all increased compared with numbers in the non-treatment zone.
All three species are quick breeders but are also easily exposed to attack. "In this respect they are like canaries in the coalmine and can give us an early indication if pest control is working."
Possum and rat numbers are dwindling, and have stayed low in the three years since the operation began.
"We are making a major investment in monitoring to assess the long-term results of this operation on a range of predators," Dr Griffiths said.
"If we can keep predator numbers down, it gives native bird populations an opportunity to breed successfully."
The eradication programme involves dropping non-toxic "blank" baits first, so pests get used to them before the poison is dropped.
Drops are usually made by helicopters using GPS at a rate of about three pellets across an area the size of an average three-bedroom house. Dyed dark green and treated with a cinnamon lure, the baits attract possums but repel birds.
The poison has a high hit rate, killing 90 per cent of rats and 98 per cent of possums in target zones.
Project Kaka measures flora and fauna across three treatment sites to determine the medium to long-term effects of repeated pre-fed 1080 drops on the forest's ecosystems.
The poison is made from sodium fluoroacetate, and works by disrupting the metabolic pathway by which animals extract energy from food. It leads to death from cardiac or respiratory failure.
Dr Griffiths says the poison is particularly suited for use in New Zealand because, unlike other countries, it has no native ground-dwelling mammals that can be affected by its use.
DOC Wairarapa ranger Sandra Burles has been on the ground monitoring and co-ordinating drops. She is also overseeing a group of "ground control" volunteers who are bolstering the aerial 1080 assault by trapping pests at Donnelly Flat, the eastern gateway to Mt Holdsworth, which attracts 35,000 visitors every year.
The team focuses on areas near walking tracks, setting traps for rodents, mustelids and possums. In the first 10 days of trapping they caught 90 possums - now the pests are tracking at very low numbers, with traps coming up empty in and around Donnelly Flat.
Rat, possum and stoat numbers will be controlled every three years, with the next 1080 drop scheduled for spring 2013.
AHB southern North Island programme manager Alan Innes said the project was critical in preventing TB-carrying possums in the southern part of Tararua Range migrating north into TB-free areas. "By working with DOC, we were able to knock out a much greater chunk of the possum reservoir, as well as making sure we maximised benefits to biodiversity."
Over time, the team hopes sustained pest control in the ranges will let rare species such as whio, robin and kiwi flourish in the Project Kaka sanctuary.
BY THE NUMBERS
98 per cent of possums are killed in an average 1080 operation
$18 the cost per hectare to target rats, stoats and possums with 1080 across 22,000ha in Tararua Forest Park
$60 the cost per hectare of using ground control to just target possums across 22,000ha in Tararua Forest Park
4 the number of cereal baits that would fall on an area of bush the size of a doubles tennis court
6 per cent of total conservation lan
For more information, see 1080facts.co.nz
The Dominion Post