Enemy recognition and response in New Zealand robins
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
The ability of robins, Petroica australis, to recognise and learn about a mammalian predator (stoat, Mustela erminea) was studied during the 1989 and 1990 robin breeding seasons, on Motuara Island (no stoats present) and at Kowhai Bush, Kaikoura (stoats present). I quantified the natural nest-defence responses of robins towards the stoat and a non-threatening control (a box) in both study areas. In the mainland population, all behaviours measured were given at greater rates by robins faced with the stoat compared to the box. In contrast, island robins responded about equally to the stoat and box, and at a level that was similar to the responses of mainland robins towards the box. These results suggest that mainland robins have learned to recognise and respond to stoats as enemies, and that the low nest-defence responses of the inexperienced robins may be typical of the responses of New Zealand endemic birds prior to the arrival of mammalian predators. I trained robins on Motuara Island to respond to a stoat as an enemy using an artificial training technique, and tested their response one day later. All robins trained using conspecific training regimes gave nest-defence responses to the stoat at a level significantly higher than robins either not trained, or trained using an interspecific regime. Training using robin mounts and alarm calls, or just robin alarm calls resulted in the highest learned response, whereas training using distress calls resulted in an intermediate learned response. These results indicate that artificial training of birds in field situations may be an effective way to improve enemy recognition ability and enhance nest-defence responses. I attempted to test the ability of robins to transfer nest-defence behaviours between generations by cultural transmission, but survival of robins was very low between seasons and insufficient data were collected to answer this question. The intensity of response of robins towards the stoat at each nest was compared with six context-related variables. Of 63 comparisons only two were significantly correlated, suggesting that the intensity of robin nest-defence responses were not dependent on these context-variables.