Warning calls are a widespread adaptation, used to inform other individuals about the presence of a potentially dangerous situation. However, these signals are not always given in response to danger and individuals can emit false warning calls in order to gain access to limited resources, such as food. Thus, species where individuals use false warning calls should have evolved rules to judge caller reliability. While this adaptation has been shown in mammals, it is unknown whether this also occurs in birds, and which criteria individuals use to trust warning calls. We investigated how social cognition affects the response to warning calls through a field experiment with a bird species that lives in stable groups, the Siberian jay (Perisoreus infaustus). We exposed dominant breeders to warning calls of former group members and unknown individuals, given towards perched hawks. Breeders immediately reacted to warning calls of former group members and escaped to safety. However, in response to warning calls of unknown individuals, breeders were much slower in responding. These results suggest that Siberian jays use social cognition to assess caller reliability and reduce the risk of deception.