A predator-elicited song in the splendid fairy-wren: warning signal or intraspecific display?

Predator-elicited vocalizations are typically thought to function as alarms to conspecifics or as deterrents to predators. In splendid fairy-wrens, Malurus splendens, ‘Type II song’ is commonly elicited in response to vocalizations of the grey butcherbird, Cracticus torquatus, a potential predator of both nestlings and adults. We examined the context of Type II songs and investigated possible antipredator functions of this vocalization using mount presentations of predators at nests, playbacks of Type II songs to females in the field and playbacks of Type II songs to nestlings. Males did not give Type II songs in response to silent mount presentations of predators at the nest, females ignored Type II songs played in the field and nestlings ignored Type II songs played at the nest. Using playbacks of butcherbird calls to males in the presence of predator and nonpredator mounts, we found that males were not more likely to give Type II songs when a predator was near the nest. Despite being commonly uttered in response to predator calls, this vocalization does not appear to be an alarm or predator deterrent. We suggest that the song is a form of male advertisement.