Migrant and resident birds adjust antipredator behavior in response to social information accuracy

Animals can reduce their uncertainty of predation risk by attuning to antipredator behavior of others or assessing the risk for themselves. Although it has never been empirically examined in the context of predation, we predicted that animals combine information gleaned from others with their own sampling experience to estimate risk. To test this prediction, we assessed the state-dependent mobbing responses of migrant and resident songbirds at a fall migration stopover site in eastern Canada to stimuli simulating a range of predation risk situations. We presented individuals with social cues in the form of playbacks of black-capped chickadee (Poecile atricapillus) mob-calls conveying graded information about predator size in combination with a predator model (one of two owl species) that rendered the social information either correct or incorrect. The response did not differ based on migratory state; both migrant and resident birds stayed longer at experimental trials when presented with erroneous social information. In particular, response duration of birds presented with a low-threat chickadee mob-call and a high-threat model (understating the risk) was substantially longer than the response to other low-threat call trials, suggesting that individuals were capable of Bayesian updating by devaluing the social cue and acting on their own assessment. Copyright 2009, Oxford University Press.