A heads-up on danger: a novel avian vigilance call changes subsequent responses to alarm calls

Gaining information about predators is critical when determining an appropriate antipredator response. Many species obtain social information from alarm calls, prompting fleeing or mobbing, but personal vigilance also provides detailed information about the current threat level. The two sources of information on danger may interact in complex ways, but this has rarely been examined. Using a series of field experiments, we first tested the function of an undescribed ‘seet’ vocalisation given by superb fairy-wrens, Malurus cyaneus, in response to predators and found that it incites vigilance in conspecific receivers. We then examined whether hearing these calls changes the threshold for response to subsequent aerial alarm calls (warning of airborne predators), either by reducing responsiveness, because individuals have more personal information, or priming individuals to respond more strongly to alarm calls. Fairy-wrens reduced their response to more urgent aerial alarm calls that followed seet calls. There was no difference in immediate response to less urgent aerial alarm calls, but individuals who did not flee were more vigilant if the alarm call followed a seet call. Our work demonstrates contextual variation in response to alarm calls, providing rare evidence that responses to these warning signals can differ based on prior calls from conspecifics, which provides an example of birds integrating social and personal information in an antipredator context.