Short-Term Variations of Dialects in Short Songs of Two Species of Colonial Caciques (Cacicus)
Résumé
The vocalizations involved in social communication of many oscine species present dialectal variants in vocalizations involved in social communication. Different hypotheses predict the function of these dialects: the "local adaptation" hypothesis, the "social adaptation" hypothesis and the "epiphenomenon" hypothesis. The social adaptation hypothesis predicts a rapid change in local dialects adjusted to each colonial variant via vocal sharing of constantly drifting song types. Here we investigated the dialect temporal variations of two colonial Cacicus species as we know that spatially-restricted dialectical variants, probably linked to social organization, exist in these species. Sound recordings were collected in the field, focalising on a series of nesting colony trees followed over several years. Songs were analysed from sonograms and their temporal and frequency parameters were compared. The fact that we observed short-term variations of colonial dialects tends to support the hypothesis of a culturally acquired colony-specific vocalization in both species.