Siberian jays help conspecifics in distress regardless of social familiarity

Helping behaviour has evolved across taxa and contexts, and shows considerable variation between individuals. While the role of kinship in modulating helping is established, recent studies highlight the importance of social bonds between actors and recipients. Theoretical and empirical work in humans and other animals shows that stronger social bonds can increase the likelihood of helping. Here, we assessed the role of social bond strength in wild Siberian jays (Perisoreus infaustus). Using playbacks of distress calls, we investigated whether individuals responded more strongly to calls from those with whom they shared stronger bonds. We exposed focal individuals to distress calls from a group member and an unfamiliar individual, alongside controls. Focal individuals responded strongly by approaching the speaker and vocalising, including producing distress calls. Although individuals modulate responses based on caller identity in other contexts, they responded similarly to distress calls from group members and unfamiliar birds, and responses did not vary with bond strength. This indiscriminate response to distress calls suggest that Siberian jays either cannot differentiate individuals based on distress calls, or respond regardless of their relationship with the distressed bird. We discuss how indiscriminate responses can be adaptive in a social bird under high predation pressure.