In 1996 an eradication operation against two species of rats (Rattus norvegicus and R. exulans was conducted on Kapiti Island (1965 ha) and its small offshore islands. Trials with non-toxic baits had been carried out to help determine the risks to non-target species, and research was undertaken to collect baseline data for measuring the response of vegetation, invertebrates, reptiles and birds to the removal of rats.
The anticoagulant rodenticide brodifacoum is widely used to eradicate invasive rats from islands for the protection and restoration of populations of native species. However, brodifacoum is also highly toxic to birds. We report the first apparent case of secondary brodifacoum exposure and subsequent poisoning in nestlings of an insectivorous passerine, the Stewart Island robin (Petroica australis rakiura). Thirteen dead nestlings were collected 3–4 months after brodifacoum bait was applied to eradicate rats from Ulva Island, New Zealand.