Siberian Jays (Perisoreus infaustus) live year-round in northern Palearctic boreal forests, usually in groups consisting of a breeding pair and several non-breeding conspecifics that may or may not be related. Predation by Goshawks, Sparrowhawks, Hawk Owls, and Ural Owls is the main, if not sole, cause of mortality in Siberian Jays, and thus this species has evolved a repertoire of antipredator behaviors that benefit both the individual, and nearby kin group members (“nepotistic”). In a recent paper, Griesser (2007) describes situation-specific calls that allow a Siberian Jay to inform kin group members of different hawk behaviors, and thus elicit responses that reduce mortality.
Siberian Jays, Perisoreus infaustus
From Naumann (1905), “Naturgeschichte der Vögel Mitteleuropas”
Griesser describes three distinct phases of the hawk hunting sequence: perched on a tree and scanning for prey, search flights to the next perch, and surprise attack using vegetation as a cover. The figure below shows the situation-specific calls used by Siberian Jays for a perched, searching (alert), or attacking hawk. The researcher used a perched hawk model, an attacking hawk model, and a control Blue Jay model to confirm the specificity of these calls. To test the hypothesis that information about hawk behavior (perched, searching, or attacking) is conveyed to other group member by these calls, Griesser played back the calls to random pairs of Jays foraging at a feeder. He found that the responses to the playback calls matched the behavior patterns following real hawk encounters, or encounters with the hawk models. For example, playback of alert calls for a searching hawk caused the foraging jays to fly to the closest cover, freeze, and engage in passive predator-search behavior. The control calls used for these playback experiments were the social foraging vocalizations known as “pickering”.
Situation-specific calls in Siberian Jays (Griesser, 2007)
Griesser discusses other examples of antipredator calls in birds and mammals, noting that these calls transmit information about predator type and the urgency to respond, whereas the calls of the Siberian Jays signal specific information about the different behaviors of a particular predator. He speculates that such predator behavior pattern-specific signals have evolved in other vertebrates, including Diana monkeys and several bird species, but have yet to be investigated thoroughly.
GRIESSER, M. (2008). Referential Calls Signal Predator Behavior in a Group-Living Bird Species. Current Biology, 18(1), 69-73. DOI: 10.1016/j.cub.2007.11.069