You can come closer, but don’t look at me. Predation risk assessment in urban birds relies on resolution of subtle cues (#852)
Accurate risk assessment allows animals to modulate their vigilance and responses to intruders. Urban animals need to be sufficiently reactive to optimize survival, but save energy when there is no immediate threat. We predicted that urban birds show heightened risk resolution, discriminating between levels of risk represented by an intruder. We examined the responses of urban and rural birds when the intruder that either had his direction of attention focused on the bird, compared with approaches when his attention was directed away from the focal bird. We tested four Australian bird species which usually forage on the ground in the open (galah, Australian magpie, magpie-lark and Australian raven). For all four species, urban birds reacted differently according to the direction of attention of the human intruder: they were less likely to move away from an intruder that was not looking at them, compared with when his direction of attention was focused on the bird. By contrast with urban birds, rural birds were more sensitive to the intruder’s presence (were more likely to flee, with longer alert and flight initiation distances), whether his direction of attention was directed at the birds or not. Rural birds react before the human approaches close enough for the bird to distinguish whether the intruder was watching them or not. By contrast, urban birds have heightened risk resolution, being attuned to subtle cues that reflect level of exposure or risk. They can therefore adjust their reactivity accordingly, saving energy and optimizing foraging opportunities.