Meeting Abstract
Optimal escape theory predicts that animals should flee from predators when the cost of staying outweighs the cost of flight. Potential costs and, consequently, antipredator responses then can be expected to vary under different conditions, such as with the perceived level of the threat or according to individual condition. Nectar-feeding birds typically have a poor capacity for energy storage and thus should exhibit robust diel variation in antipredator behavior that is driven by foraging motivation. Antipredator responses are commonly measured using flight initiation distance (FID), the distance at which an individual flees from an approaching predator. Using the nectarivorous New Holland honeyeater (Phylidonyris novaehollandiae) we hypothesized that FID varies throughout the day, predicting shorter FIDs in the morning and evening than at midday, following from and in preparation for the overnight fast, with greater FIDs at midday. In addition, we asked whether escape mode (hop vs. flight) varied throughout the day, according to their presumed nutritional status and the energetic cost of the escape mode. We found evidence of a quadratic relationship between FID and time of day, with relatively shorter FIDs in the morning and evening than at midday (F3,82 = 16.41, R2 = 0.35, p < 0.001). Honeyeaters were increasingly likely to fly to escape as the day progressed (OR = 1.27, CI = 1.11 – 1.49, p < 0.001). These results suggest that New Holland honeyeater FID responses support economic models of optimal escape theory, varying with individual energetic needs over the day.
