Male courtship vocalizations as cues for mate choice in the Satin Bowerbird (Ptilonorhynchus violaceus)

-Male Satin Bowerbirds (Ptilonorhynchus violaceus) court females at specialized structures called bowers. Courtship includes a complex pattern of vocalizations in which a broad-band, mechanical-sounding song is followed by interspecific mimicry. We studied the effect of male courtship displays on male mating success in Satin Bowerbirds. Data from 2 years of field research showed low between-male differences in mechanical components of courtship song and high variability between males in mimetic singing. Older males sang longer and higher-quality bouts of mimicry than did younger males. In one year, courtship song features were correlated with male mating success. The results suggest that female Satin Bowerbirds use male courtship vocalizations in their mate-choice decisions. We discuss hypotheses about assessment of male age and dominance from courtship vocalizations and suggest that these songs have evolved as a result of selection for male display characteristics that provide females with information about the relative quality of prospective mates. Received 27 June 1985, accepted 20 September 1985. MALE Satin Bowerbirds (Ptilonorhynchus violaceus) build specialized structures called bowers that are used as sites for courting females and for mating (Vellenga 1970, Donaghey 1981, Borgia 1985). Females raise their young unassisted by males, and males do not associate with females after mating. Males decorate their bowers with a variety of natural objects and attempt to steal decorations and destroy the bowers of other males. Much effort has been focused on understanding the role of the bower and its decorations in female mating decisions. Borgia (1985) demonstrated a skewed distribution of matings among male Satin Bowerbirds, differences among males in bower decoration and construction, and a consistent pattern of female preference for males with well-constructed and well-decorated bowers. In addition, male mating success is influenced negatively by bower destruction and decoration-stealing (Borgia 1986a, Borgia and Gore 1986). Male courtship vocalizations are another component of male sexual display that may have important effects on female mating decisions. Male courtship is intense, involving dance movements and postures that are coordinated with the simultaneous production of complex vocalizations. The female crouches within the bower, closely observing the male during the display, and controls the outcome of the courtship either by signaling her willingness to copulate or by flying away. Given the complexity of male display and the attention females pay to displaying males, it is likely that male displays have an important effect on female mating decisions, yet there have been no detailed studies of display in any bowerbird