Rifleman (Acanthisitta chloris sp.) population responses to aerial 1080 (sodium fluoroacetate) predator control in beech forests

Aerial 1080 is the primary method of large-scale predator control of ship rats (Rattus rattus) and stoats (Mustela erminea) in the southern beech (Nothofagaceae) forests of mainland New Zealand. Measuring outcomes for native species of such predator control is essential to ensuring wise use of conservation resources. Rifleman/tītitipounamu (Acanthisitta chloris sp.) are a common endemic passerine that are declining, even in large remote forests. We studied annual survivorship and nest success of tītitipounamu in beech forest in the Tararua Ranges, Marlborough Sounds, and South Westland in response to aerial 1080 predator control. We monitored 72 individuals and 337 tītitipounamu nests from untreated and treated sites, which included seven aerial 1080 operations. Our results show strong benefits of aerial 1080 for tītitipounamu from both improved nest success and annual survivorship, with benefits for nest success extending to the second breeding season after an aerial 1080 operation. Nest success ranged from < 58% without treatment to > 77% with treatment. Annual survivorship in non-treatment areas was 19% and 43% and in treatment areas was 62% and 84% for juveniles and adults, respectively. Population modelling indicated that predator control approximately every 3 years is necessary for tītitipounamu population persistence.