Higher sensitivity to human gaze under additional cost and risk: a field study on Azure-winged magpies

In predator-prey interactions, various factors affect the prey's perception of risk and decision to flee. Gaze sensitivity, the ability to react to the presence, direction, or movement of the head and eyes, has been reported in many birds and they could recognise not only the head direction but the subtle difference in eye direction. But few studies focused on variation in sensitivity to human gaze in relation to other risks and costs. Here, we studied the influence of human gaze on the escape behaviour of Azure-winged magpies ( Cyanopica cyanus ) and investigated the effects of breeding state and directness of approach on gaze sensitivity. In Experiment 1, we tested whether magpies showed different sensitivity to human gaze according to age class and breeding state when being approached directly. The results showed that the breeding state could affect the flight initiation distance (FID), with adults in the breeding season having a shorter FID. Meanwhile, only adults were found to be averse to direct human gaze and juveniles showed no sensitivity, implying that gaze aversion was not innate. In Experiment 2, we conducted three different gaze treatments on adult magpies in the breeding season under three bypass distances (0m, 2.5m, 5m). The results showed that directness of approach had no effects on FID, while the sensitivity to human gaze differed under three bypass distances. Adults could clearly recognise human head and eye direction at a certain bypass distance (2.5m). Our study reveals the cognitive ability of Azure-winged magpies to human head and eye direction and the effects of additional cost and risk, which may provide further insights into human-wildlife interactions, especially for birds in urban habitats.