Following widespread beech seeding across Fiordland in early 2016, and a recorded increase in rat numbers, DOC treated six sites with aerially applied 1080 as part of the national Battle for our Birds programme, including the Eglinton and Arthur Valleys, the Waitutu Forest and areas of the Kepler.
Greg Lind, DOC Operations Manager for Fiordland, said populations of vulnerable species such as mohua, kākā, kea, whio/blue duck, Fiordland tokoeka and native bats did far better with aerial predator control than without it.
“Monitoring has shown mohua productivity in the Eglinton Valley was considerably greater in the 1080 treatment area. Recorded fledging success in the 2016/17 season was 68-84%, which is over two mohua chicks per adult pair.”
“This is compared with the non-treatment area where fledging success was recorded at around 40% - less than one chick per pair,” Greg Lind said.
A similarly encouraging result was recorded in the Iris Burn Valley of the Kepler mountains, home to a population of nationally endangered long tailed bats. Bats are extremely vulnerable to predation, and with no successful methods currently established to translocate populations to safer areas, protecting established roost sites are vital.
Aerial 1080 operations were carried out in the Iris Burn in response to the 2014 and 2016 beech masts. In 2013, the monitoring team recorded 32 females. By 2016 there were 57. Nearly all females recorded last year were lactating, a good indication of there also being baby bats at the females’ roost sites.
In the Waitutu Forest, the proportion of female kākā has increased almost four-fold since intensive predator control started. Trapping and poisoning for stoats, rats and possums, including three treatments of aerially-applied 1080 over up to 30,000 hectares have resulted in a turnaround in the parrot’s fortunes with female kākā rebounding and young birds on the rise again.
Annual bird counts at over 700 points in the forest also show an increase in other forest birds such as robin and kākāriki.
Similarly, an intensification of stoat trapping in the Murchison Mountains has resulted in no recorded predation of takahē in the area during, and following, the 2016 mast event.
Prior to 2010, less than 0.5% of Fiordland National Park received landscape scale possum and rat control. DOC’s Battle for Our Birds campaign saw this increase to 7% in 2014, and to 8.5% (100,000ha+) in 2016.
Two further aerial operations will take place in 2017, in the Upper and Lower Hollyford Valleys, and the Cleddau catchment, to target possums, rats and stoats.
“The operations will take place between August and September,” Greg Lind said. “This is timed to provide the best possible environment for birds during their breeding and hatching season.”
“The aerial operations complement current trapping programmes underway in the Hollyford and Cleddau areas,” Greg Lind said.
Species likely to benefit from aerial predator control in these areas include whio, Fiordland tokoeka (kiwi), mohua, rock wren, South Island kākā and Fiordland crested penguin. These birds are all highly vulnerable to rat and stoat predation, as well as possum disturbance and sometimes predation during the nesting period.
A number of threatened mistletoe species, highly vulnerable to possum browse, are also found in the area.
Battle for our Birds is one of many programmes that support DOC’s goal of protecting threatened species and making New Zealand predator free by 2050.