Abstract <p>Auditory risk recognition is ubiquitous in birds. Recent studies suggest that birds can learn to recognize acoustic risk cues socially, by associating novel sounds with known alarm cues. However, factors affecting the extent to which birds learn to recognize acoustic cues reflecting predation risk remain poorly understood. Here, I tested whether social transmission of auditory risk recognition is threat-sensitive. In a playback experiment, I trained wood warblers (<i>Phylloscopus sibilatrix</i>) to recognize previously unfamiliar sounds as cues of a threat by simulating anti-predator responses of conspecifics to these sounds, with conspecific responses indicating either high or low risk. I found that most wood warblers learned to recognize trained sounds as risk cues but only when playbacks simulated high predation risk. Furthermore, I found that the intensity of learned anti-predator responses decreased during social transmission. Learning by associating previously unfamiliar sounds with known alarm cues is therefore threat-sensitive, with individuals acquiring anti-predator responses to novel sounds depending on the strength of the anti-predator responses of conspecifics. In the wild, threat-sensitive social transmission likely prevents maladaptive learning via indirect risk cues, allowing individuals to minimize the costs of incorrectly associating neutral sounds as cues of a threat.</p> Significance statement <p>Risk recognition based on acoustic cues is common in animals and has important ecological consequences for prey’s behavior, physiology, and life history traits, which in turn further scale-up to affect prey’s survival and demography. Many birds, for example, assess predation risk based on acoustic cues, such as predator vocalizations or heterospecific alarm calls. However, how they learn to recognize that specific sounds are cues of a threat remains largely unknown. This study shows that birds learn to recognize previously unfamiliar sounds as risk cues socially, by associating them with conspecific alarm calls. Moreover, they learn only when conspecific responses indicate high risk. Under natural conditions, such threat-sensitive social transmission likely allows individuals to minimize the costs of incorrectly associating neutral sounds as cues of a threat when learning via indirect risk cues.</p>