Calling in an acoustically competitive environment: Duetting male long-tailed manakins avoid overlapping neighbours but not playback-simulated rivals

Animals that live in communication range of multiple conspecific receivers have the potential to interfere with their neighbours\u27 signals, or to avoid interference by signalling at different times. We used both an observational and experimental approach to study signal timing in lekking tropical birds. We recorded duetting pairs of male long-tailed manakins, Chiroxiphia linearis, during periods when two neighbouring pairs were calling concurrently, and during playback of a simulated pair of nearby rival males. We used three complementary analytical techniques to evaluate whether birds varied the timing of their duet calls relative to nearby animals: circular statistics, resampling analysis and duty cycle models. Our analyses reveal that long-tailed manakins produce duets with nonrandom timing with respect to the calls of their rivals. During natural bouts of concurrent calling, all three analytical techniques revealed that manakins time their duets to avoid overlap. In response to playback, males showed more variable strategies. Males overlapped duets more during playback than they did under natural conditions and, in some cases, they overlapped playback duets at higher levels than would be expected based on chance. Our study shows that males alter the timing of their calls in response to the vocalizations of others around them, and it uncovers similarities in the acoustic signalling behaviour of lekking birds relative to the better-studied signalling behaviour of territorial birds. We also show that different null models of signal timing yield different insights into animal signalling behaviour. © 2012 The Association for the Study of Animal Behaviour