Ontogeny of the Vocal Repertoire in the Willow Tit Parus montanus

Abstract

Results of a long-term study of the Willow Tit Parus montanus population in the birch region at Venabu, Ringebu (61?39'N, 10008'E) in Central Norway, are presented. After fledging, the juvenile Willow Tits were dependent on their parents for another 2-3 weeks. During that period, they developed their vocabulary, which was nearly complete before independence. The syntax and ontogeny of eight main vocalizations (including the song) are described and illustrated by spectrograms. Non-aggressive calls developed before those with an aggressive content, the latter being postponed to the end of the period of parental dependence, or immediately thereafter. This pattern is probably adaptive. For comparison, also the corresponding adult vocalizations are described and illustrated by spectrograms. Besides the main sounds, a special puretone note, which evidently is restricted to the Willow Tits at Venabu and maintained in the deme by learning, is described. It is suggested that subsong has an important function in the process of vocal development.