The kea (Nestor notabilis) and other New Zealand forest birds are threatened by predation by introduced mammals. Mammal control for biodiversity conservation in New Zealand commonly involves the aerial application of cereal-pellet baits containing sodium fluoroacetate ('Compound 1080'), but its effectiveness for kea conservation has not previously been assessed. This study examined the effects of aerial 1080 on the reproductive success of kea in a lowland rimu forest on the West Coast of New Zealand's South Island. We measured three parameters which collectively describe annual reproductive success (nesting frequency, nest survival and final chick count), within a Before-After-Control-Impact experiment. The Impact site was a 30 000 ha area over which 1080 baits were aerially applied in the spring of a rimu (Dacrydium cupressinum) mast year (i.e. with heavy seedfall), with the After phase of the experiment lasting for two kea nesting seasons. The invasive mammals ship rat (Rattus rattus), brushtail possum (Trichosurus vulpecula) and stoat (Mustela erminea), which are potential predators of kea nests, were much less abundant in the Impact site after 1080 application, on the basis of standard indexing techniques. There was strong statistical support for an effect of aerial 1080 on kea nest survival. Aerial 1080 improved the odds of daily nest survival by a factor of 9.1 at the treatment site. Nest survival rates in the Control and Impact sites, before the application of 1080, were 21% and 46.4%, respectively. After the application of 1080 to the Impact site, nest survival increased to 84.8% in this site, whereas it declined to 12.2% in the untreated Control site. This substantial positive effect of aerial 1080 on kea nest survival is attributed to the effective control of mammalian nest predators, particularly the secondary poisoning of stoats.
The kea (Nestor notabilis) is a highly intelligent and adaptable omnivorous New Zealand parrot. These traits potentially put kea at risk of poisoning during vertebrate pest poisoning operations. However, as kea fall prey to introduced pests, they also gain from pest control, creating a cost-benefit situation. Pest control in kea habitat is mainly by aerial 1080, the distribution of sodium fluoroacetate poison pellets by helicopter. Understanding the net outcome for kea of this pest control method is extremely important because kea are endangered and aerial 1080 use is controversial. We use 222 monitoring cases of individually marked kea at 19 aerial 1080 operations to model kea survival of aerial 1080 operations with respect to five variables. Proximity to human-occupied sites where kea scrounge human food was inversely related to survival; the odds of survival increased by a factor of 6.9 for remote kea compared to those that lived near scrounging sites. High survival in remote areas is explained by innate neophobia and a short field-life of prefeed baits, which together preclude acceptance of poison baits as familiar food. Elevated risk to kea living near scrounging sites is explained by learned neophilia, possibly exacerbated by lead poisoning. Survival was also related to the history of aerial 1080 treatment at a site; the odds of survival increased by a factor of 21.3 at sites with repeated operations compared with first time treatments. This effect is possibly due to selection for neophobic phenotypes. We suggest that 1080 poisoning risk management for kea should focus on reducing human food availability through an advocacy campaign. If most kea have not been fed by humans, then the long term outcome of the South Island aerial 1080 programme should be positive for the kea.
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