Female preferences drive the evolution of mimetic accuracy in male sexual displays

Abstract

Males in many bird species mimic the vocalizations of other species during sexual displays, but the evolutionary and functional significance of interspecific vocal mimicry is unclear. Here we use spectrographic cross-correlation to compare mimetic calls produced by male satin bowerbirds (Ptilonorhynchus violaceus) in courtship with calls from several model species. We show that the accuracy of vocal mimicry and the number of model species mimicked are both independently related to male mating success. Multivariate analyses revealed that these mimetic traits were better predictors of male mating success than other male display traits previously shown to be important for male mating success. We suggest that preference-driven mimetic accuracy may be a widespread occurrence, and that mimetic accuracy may provide females with important information about male quality. Our findings support an alternative hypothesis to help explain a common element of male sexual displays.

Figure 1

Spectrograms of (a) model species' calls, (b) high-accuracy and (c) low-accuracy mimetic calls. (i) D. n., Dacelo novaeguineae; (ii) M. l., Meliphaga lewinii; (iii) C. c., Corvus coronoides; (iv) C. g., Cacatua galerita; (v) C. f., Calyptorhynchus funereus.

Figure 2

Scatterplots showing the linear regressions of male mating success on (a) mean mimetic accuracy and (b) mean number of species mimicked.