The Department of Conservation completed its Battle for our Birds aerial 1080 pest control operation in the Dart, Route Burn and Caples valleys on Sunday 31 August.
This operation aims to protect local populations of the mōhua (yellowhead), kākāriki (parakeet), whio (blue duck), tuke (rock wren) and kākā. Each of these bird species are nationally threatened and the kākāriki exists only in small isolated populations.
The application of biodegradable 1080 poison baits over nearly 20,000 hectares in the Dart, Route Burn and Caples valleys follows treatment of the area with non-toxic “pre-feed” bait last Tuesday (26 August).
Both the pre-feed and poison operations followed stringent safety procedures and buffer zones were in place around major waterways such as the Dart River, Beans Burn, Rock Burn, Route Burn, Caples River and Lake Sylvan. All DOC huts, camping grounds and public amenity areas were also avoided.
DOC rangers have inspected and cleared almost all the tracks that were closed while the operation was underway. Due to avalanche risks the following tracks have not yet been checked and they remain closed until further notice: Upper Route Burn North Branch, Rock Burn (from junction of Sugarloaf track); Beans Burn and Upper Fraser Creek.
Warning signs advising the public about the dangers of the pesticide are in place at all normal access points to the treatment area. Signs will also be in DOC huts and at camping areas. Please observe the instructions on the warning signs for as long as they remain in place.
For more information on DOC’s Battle for our Birds pest control response see: www.doc.govt.nz/battleforourbirds
The most effective method of control for a rapid response to predator threats over large areas of difficult terrain is aerially-applied sodium fluoroacetate (1080). Without this predator control many species of native wildlife could vanish from the Dart, Route Burn and Caples.
Rat plagues in beech mast (seeding) years have particularly damaged local mōhua populations in the past. Monitoring shows that mōhua were decimated in the Dart/Caples in the 2000 and 2011 beech mast years when rats were not effectively controlled - in 2011 about 75% of mōhua were lost to predation. In 2006 and 2009 when these areas were treated with aerial 1080 mōhua populations remained steady.
Over 500 tracking stations are in use across the Dart, Route Burn and Caples valleys to survey rat numbers. From May to July the data showed strong increases in rat abundance, similar to the last pest plague seen in 2011. If not controlled these rising rat numbers would lead to higher numbers of stoats, which also predate on native wildlife.
Monitoring the effects of the pest control operation will be undertaken in coming months to measure the knock-down of rats.
The poison baits are 3 cm long, cylinder shaped and dyed green to deter birds. Only 0.15% of the bait is 1080 (9 milligrams). The baits were deployed at 1 kilogram per hectare, or about one 6 gram bait per 60m2. Helicopters distributed the baits according to predetermined flight paths controlled by GPS.
Warning signs are in place at all normal access points to the treatment area, and huts, camping and public amenity areas. Observe the instructions on the warning signs. When these signs are removed you can resume normal activities in the area.
The Dart, Route Burn and Caples is one of 25 confirmed Battle for our Birds operations that will use aerially applied 1080 over about 650,000 hectares of conservation land to knock down rising predator numbers fuelled by unusually heavy seeding in South Island beech forests. It is the sixth operation to be completed so far.