Vocal mimicry by a passerine bird attracts other species involved in mixed-species flocks

Little is known about how vocal mimicry affects the behaviour of members of other species. Such effects might, however, be especially likely in mixed-species flocks in which birds of some species directly benefit from the behaviour of members of other species. In mixed-species flocks in Sri Lanka, the greater racket-tailed drongo, Dicrurus paradiseus, mimics the songs and contact calls of other flock participants. We hypothesized that this mimicry attracts other species, as drongos are well known to increase their foraging efficiency in association with other species. Consistent with the predictions of this hypothesis, we recorded the most mimicked vocalizations during the rare occasions in which drongos were outside of flocks. In addition, we performed a playback experiment, which showed that taped drongo vocalizations that included song mimicry were more than twice as attractive to birds of other species as were taped vocalizations that lacked mimicry. We suggest that mimicry is a way in which drongos manage the behaviour of flockmates in what appears to be overall a mutualistic relationship.