Complex communication signals: The case of the Blue-black Grassquit Volatinia jacarina (Aves, Emberizidae) song. Part I - A structural analysis

Abstract

The song of the Blue-black Grassquit Volatinia jacarina is different for every individual and the structural differences between individuals are quite complex. Samples of songs from different Brazilian localities, as well as from Venezuela and Mexico, were studied through a comparative analysis of their sonograms. From the structural point of view, the results show a song composed of a single note that is compacted in a "window" between 2 and 13 kHz and rarely occupying more than half of a second. The note is essentially pure and is repeatedly uttered with a high level of fidelity. A global frequency modulation decreases from the beginning to the end of the song. The main song components are referred to as "Blocks" and are of three types: "Vibrations" (Buzzes or Vibratos), "Arabesques" (complex notes) and "Isolated Modulations" (simple syllables). Among other characteristics are double voices, which are quite diverse and probably function as codes for individual recognition. This song is considered a special case where a signature system has been developed to a high level of inter-individual variability.