Repellents to deter New Zealand's North Island robin Petroica australis longipes from pest control baits

Abstract

North Island robins, Petroica australis longipes, are among the non-target animals at risk during poisoning operations aimed at introduced mammalian pests in New Zealand. Adding an avian repellent to the bait may reduce the risk to native birds. In this study we report on two experiments that aimed to: (1) refine a methodology for testing repellents; and (2) determine the effects of a repellent combination on bird feeding behaviour. In Experiment 1, a highly preferred base material (in which repellents could be incorporated) was identified from the choices made when robins were presented simultaneously with cereal, carrot and dough materials over 4 consecutive days on a test arena on the forest floor. Robins pecked at and ate all materials, but consistently directed more pecks at dough (P<0.001), so this material was selected for use in the subsequent study. In Experiment 2, robins were offered repellent treated (green and surface coated with a combination of d-pulegone and Avex™) and standard (green and coated with cinnamon oil; the bait formulation currently used for pest control operations in New Zealand) dough in choice tests over 4 days. The dough had either been sprayed with or dipped into the repellent combination. Robins pecked at standard dough more frequently than at repellent dough (P<0.05), with the frequency of pecking at repellent dough declining (P<0.05) over the four days. Male robins offered dipped dough pecked at the repellent dough more frequently than females. On occasions the base material was removed from the arena: standard dough removed was consumed readily but repellent-treated dough was not. The results demonstrated that the combination of d-pulegone and Avex effectively deterred robins from feeding. Green dye and cinnamon oil did not prevent feeding on cereal, carrot or dough by robins, and thus cannot be considered as effective repellents. Since d-pulegone and Avex were effective in preventing feeding on a highly preferred base material they are likely to reduce the propensity for robins to feed on toxic possum baits.