The bold bird gets the worm? Behavioural differences of South Island robins ( Petroica australis ) in relation to differing predation risk

Consistent differences among individuals in the boldness-shyness continuum have been described in a variety of species. Environments with higher levels of predation are likely to select for shyer behavioural responses, due to the increased susceptibility of being ‘fearless’ in a high-risk environment. In this study, we compared the behavioural responses in two populations of South Island robin (Petroica australis), one of which is sympatric with a range of introduced predators (Kaikoura mainland) and one with no introduced predators (Motuara Island). We found robins on Motuara Island were significantly bolder than mainland robins. This was evidenced by robins in this low-risk environment being more likely to approach mealworms placed closer to a researcher. Robins in Kaikoura were also significantly slower than Motuara Island robins in latency (time to approach mealworms) but faster to remove five mealworms placed nearest to a researcher (handling time). These differences may be driven by bolder individuals having a disadvantage on the mainland as it exposes them to a higher risk from introduced predators. Although the extent to which these differences have a genetic basis is unknown, our results suggest that sympatry with introduced predators may favour more risk-averse behaviours in robins and other native species.