Survival of Little Spotted Kiwi Exposed to the Rodenticide Brodifacoum

Abstract

Conservation benefits of eradicating invasive species are clear, but these efforts can affect non-target species of special concern. We monitored the survival of little spotted kiwi (Apteryx owenii) during a program that eradicated Pacific rats (Rattus exulans) and Norway rats (R. norvegicus) from 1965-ha Kapiti Island, New Zealand. About 90% of the world population of this threatened bird was at risk during the poison operation. Two of 10 radiomarked kiwi died in the months following the aerial distribution of cereal baits containing 0.002% active ingredient brodifacoum. Of 50 adult birds banded before the toxin application, we found 46 still alive >6 months after the toxin application. At worst, 8% (3-19%) of little spotted kiwi were killed by accidental poisoning. Once natural mortality was taken into account, the actual toxin-induced mortality was much lower than this. The population of little spotted kiwi on Kapiti Island did not appear to be affected by brodifacoum long-term, because accidental losses were compensated by high productivity in the breeding seasons following rat eradication.