Vocal development and its differentiation in a non-songbird: The collared dove (Streptopelia decaocto)

Coo development and its differentiation was studied between the second and eighteenth month of life in captive collared dove males (N = 9) and females (N = 6). During this period eight vocal characteristics were analyzed to determine the nature of age-related changes in the spectrotemporal structure of the perch-coo. At the onset males and females produced coos with the same structure, with exception of the fundamental frequency. In males, age-related changes in fundamental frequency, stereotypy, and coo length were limited. Early stabilization of these parameters may be related to maturation of the syrinx. Vocal activity, bout length, modulation percentage and sound percentage increased, which might be caused by an age-dependent increase in testosterone. The number of harmonics decreased, which might be related to some kind of 'motor practice'. Similar to song development in songbirds, perch-coos of male doves develop gradually into more conspicuous vocalizations, showing some plasticity in form development. In contrast, in female doves none of the vocal parameters changed with age. As a result, the structure of adult female coos continued to resemble that of juveniles, as has also been shown for female song in songbirds. For several vocal parameters the developmental trajectories of male and female coos began to diverge at the age of about one year. Two to three months later the sex differences became significant. Two vocal parameters showed an age-related change in inter-individual variation: vocal activity and modulation percentage of males. These findings support the hypothesis that frequency modulations may play an important role in intra-specific communication, conveying messages about a senders sex and age.