Danger may enhance communication: predator calls alert females to male displays

Sexual displays are typically given in the absence of predators. One possible exception to this is seen in male splendid fairy-wrens (Malurus splendens), which sing display-like vocalizations (Type II song) in response to predator calls. In this study, we explored the function of this vocal "hitchhiking" using playback experiments. We documented that: 1) males responded to Type II songs of other males as if they were displays intended for conspecifics, 2) females became more attentive after hearing a predator vocalization than a control (nonpredator) vocalization, and 3) females tended to respond more strongly to Type II songs when the songs were preceded by a predator vocalization than when they were given solo. Males of all age and status classes produced Type II songs and production was not dependent on any of 3 morphological measures of male quality, so we do not find evidence to support the hypothesis that Type II singing behavior is condition dependent. Because predator calls increased female attentiveness and tended to increase subsequent response to Type II songs, it appears that males may be using predator vocalizations as alerting signals for their own conspecific-directed displays.