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A close eye is being kept on the amount of seed produced and how rodents respond to this bounty. Seed from more than 400 seed traps has been collected and is being counted, and rat levels are being checked every few months using 6000 tracking tunnels. In the Maruia valley near Lewis Pass, trigger levels have already been reached. May monitoring results showed that rats were present in about 40% of tracking tunnels – a big jump from just below 10% in February. Research shows that well-timed pest control can significantly boost kea nesting success. After rimu seeding on the West Coast, for example, kea in forest at Okarito treated with aerial 1080 raised four times the number of young as kea in a similar forest at Fox-Paringa with no predator control. While there remains some risk to kea of being poisoned by 1080 baits, this is considered to be offset by the benefits of pest control to the kea population overall, says DOC science advisor Josh Kemp. “The abundance of rodents in beech forests this year is increasing similarly to what was seen at Okarito, which means we can expect comprehensive stoat control over very large areas. It’s this stoat control that brings the big benefits to the kea population.” DOC has monitored 150 kea through ten aerial 1080 operations since 2008 and has observed 20 deaths in three of these, although none in beech forest. Kea will be monitored in two of the planned Battle for our Birds operations – in Kahurangi National Park and Abbey Rocks in South Westland – to learn more about the risk of non-target poisoning. At Kahurangi, nesting success and survival will also be measured over the two kea breeding seasons after the 1080 drop, to verify whether the benefits found at Okarito also apply in beech forests, says Josh.
Up to 40 kea will be radio-tagged prior to the large-scale Kahurangi operations in spring and will be monitored for two years and possibly a third. “It’s hoped the knock down of pests over 260,000 ha at Kahurangi will similarly boost kea numbers, as it did at Okarito,” he says. “We’re optimistic that we could get three years of stoat suppression in Kahurangi, which will be of lasting benefit to kea, as well as other species such as kiwi and whio.” DOC has recently tightened controls for aerial 1080 use on conservation land where kea may be present in a new code of practice. DOC technical advisor Michelle Crowell, who led the development of the code, says it aims to minimise the risks to kea of nontarget poisoning and ensure they benefit from stoat control as an outcome of any operation. The key change, says Dr Crowell, is to restrict 1080 operations to times when rodents are present, such as during and soon after forest seeding events, to get secondary poisoning of stoats. “Essentially, we are trying to time 1080 operations to boost kea breeding and survival to ensure we get maximum benefit for kea populations and compensate for any kea deaths from 1080 if they occur.” Another change is the lifting of restrictions on sowing baits in open areas above the tree-line so that other alpine species such as rock wren can also benefit from stoat control. The alpine boundary for pest control operations will now be determined on a caseby-case basis, weighing up the potential risks to kea and benefits to other species of pest control. “We thought that by keeping baits out of areas where they might be more visible would protect kea,” explains Dr Crowell. 19