Impact of brodifacoum poisoning operations on South Island Robins Petroica australis australis in a New Zealand Nothofagus forest

Abstract

South Island Robins Petroica australis australis were monitored through two different brodifacoum (Talon 20 P, 20 ppm) control operations targeting stoats Mustela erminea and ship rats Rattus rattus in a Nothofagus forest. Repeated observations of banded and radio-tagged territorial adult Robins were used to monitor survival from 6 to 8 weeks after poisoning. Where poison was deployed in bait feeders, 96.7% (29/30) of marked Robins definitely survived, whilst where poison was freely broadcast, only 52.2% (12/23) of marked Robins definitely survived. At the non-treatment site 85.7% (18/21) of marked Robins definitely survived. This study demonstrates that individual Robins are at risk from poisoning from exposed brodifacoum on the forest floor and therefore, probably from aerial application of brodifacoum. Further research is required to determine whether the benefit to Robin populations from successful predator control outweighs the loss of some Robins from poisoning. Conservation managers must take a wide view of the ecological community impacts when controlling introduced mammalian predators.