SEX-DIFFERENCES IN THE VOCALIZATIONS AND SYRINX OF THE COLLARED DOVE (STREPTOPELIA-DECAOCTO)

We examined differences between sexes in the structure of vocalization s and the syrinx of the Collared Dove (Streptopelia decaocto). Seven v ocal characteristics were measured to determine the degree of sex diff erences in the structure of the ''perch-coo.'' Sex differences in voca lizations occurred in vocal activity levels and spectrotemporal parame ters. Females produced fewer and shorter coo bouts. Coos produced by f emales also had a higher fundamental frequency, more overtones, a diff erent temporal pattern, and tended to be less stereotyped. Discriminan t function analysis revealed that sound percentage, followed by modula tion percentage and fundamental frequency, were best at discriminating between the sexes. Based on the magnitude of sex differences and acou stic discrimination ratios, the latter two characters are the ones mos t likely to be used for vocal sex recognition. In general, the syrinx of female Collared Doves is a reduced copy of the one found in males. Trachea size and the number of tracheal and bronchial rings had high l oadings on the principal components that showed significant difference s between the sexes. In addition to general size differences, the numb er of ventromedially thickened rings and length of the tracheosyringea l membrane also were strongly correlated with these principal componen ts. Length and height of the primary bronchi did not appear to differ between the sexes but were bilaterally asymmetrical only in males. The combination of vocal and anatomical data provides evidence that morph ological aspects contribute to sexual dimorphism in vocalizations.