Feeding by Captive Rare Birds on Baits Used in Poisoning Operations for Control of Brushtail Possums

Non-toxic plain and cinnamon-flavoured carrots and cereal-based baits used in poisoning operations for control of the brushtail possum (Trichosurus vulpecula) were offered to seven species of captive rare birds at Mt Bruce National Wildlife Centre. Some individuals of all species ate plain baits. Antipodes Island parakeets (Cyanoramphus unicolor) preferred carrot to cereal-based baits, North Island kokako (Callaeas cinerea wilsoni) and North Island saddlebacks (Philesturnus carunculatus rufusater) preferred cereal-based baits to carrots, but the other species showed no bait preference. Most baits eaten were greater than 2 g. Some individuals of all species also ate cinnamon-flavoured baits. However, cinnamon deterred North Island kaka (Nestor meriodionalis septentrionalis), Antipodes Island parakeets, and kokako from feeding on baits the first day offered, though not subsequently. Insufficient baits were eaten by North Island weka (Gallirallus australis greyi), red-crowned parakeets (Cyanoramphus novaezelandiae novaezelandiae), and Reischek's parakeets (Cyanoramphus n. hochstetteri) to determine whether they were also deterred by cinnamon. Only saddlebacks were definitely not deterred. All species except red-crowned and Reischek's parakeets probably ate sufficient to receive a lethal dose if the baits had been toxic. Baits may be made less acceptable to birds by increasing the strength or slowing the release of cinnamon, or by using a more repellent flavour. Because baits may always be acceptable to some birds, wildlife managers need to know the chances of wild rare birds feeding on baits before approving poisoning operations in areas where they occur.