The threat to native birds and bats from plague levels of rats and stoats has been eased with a successful knock-down of rodents in a recent pest control operation in Fiordland National Park.
The Department of Conservation’s Battle for our Birds operation over 11,200 hectares in the Iris Burn valley near Te Anau was targeted to protect long-tailed bat, whio/blue duck, mōhua/yellowhead, kākā and kea from rising predator numbers fuelled by beech forest seeding.
Monitoring results from 140 tracking tunnels show that rats dropped to undetectable levels from a high of 72 % following the aerial 1080 treatment last month. The mice population was also significantly reduced from 77 to 21 %.
DOC Fiordland Conservation Services Manager Lindsay Wilson said this was a fantastic result and would allow native birds and bats to survive and breed this spring.
“With this level of knock-down there will be lots of dead rodents for stoats to feed on. The stoats themselves then die from secondary poisoning so this operation should virtually wipe them out of the valley.
“This will pave the way for a good breeding season for birds and long-tailed bats without rats or stoats to attack them on the nest and in maternity roosts.
“The survival of stoat-vulnerable species such as whio, kākā, kea and young kiwi should also increase.”
The operation also targeted possums, which were at moderately high levels, and these are also expected to have been significantly reduced, said Wilson.
Meanwhile, monitoring in several other western Fiordland Battle for our Birds sites has shown variable quantities of beech seed and rodent levels.
Low beech seed and rodent levels have been recorded in the Arthur, Sinbad and upper Hollyford valleys and around Dusky Sound and therefore these planned Battle for our Birds operations will not go ahead.
Pest control operations have been confirmed for the Clinton and Lower Hollyford valleys and are due to start in coming weeks.
The Iris Burn is one of 25 confirmed Battle for our Birds operations using aerially-applied 1080 over a total of about 680,000 ha of conservation land, largely in South Island beech forests.
Six operations have been successfully completed, including in the Waitutu Forest in Fiordland National Park and Waikaia Forest in Southland.
For more information on DOC’s Battle for our Birds pest control response see: www.doc.govt.nz/battleforourbirds
- The Iris Burn pest control area is home to a number of species vulnerable to predation by rats, possums and stoats, including long-tailed bat/pekapeka, whio/blue duck, mōhua/yellowhead, Fiordland tokoeka kiwi, kea and kākā as well as more abundant forest birds such as kākāriki, robin, tomtit and rifleman.
- The long-tailed bat population in the Iris Burn is in decline and removal of rats and stoats should allow numbers to increase. Annual summer monitoring of bats will show the effects of pest control and enable more roosts to be identified to best target future protection.
- A regular monitoring programme for rat-sensitive birds such as robin, tomtit and rifleman in the Iris Burn will show their response to pest control and will indicate outcomes for rarer species like mōhua, which can’t be monitored at current numbers.
- Annual summer river surveys of whio/blue duck may also show the effect of pest control.
- Possums will be monitored in coming months to determine knock-down from the Iris Burn pest control operation.