An Analysis of the Full Song of the Blackbird Turdus merula with Respect to Message Coding and Adaptations for Acoustic Communication

Abstract

The full song of the Blackbird was analysed quantitatively by means of sonagraph, level recorder and computer. Species-specific limits of variation are given for a number of song parameters. Some of these parameters vary between individuals, others vary within individuals in two situations, viz. dawn song with heavy stimulation from rivals and evening song with weak stimulation from rivals. The parameters and the differences between the variations of the parameters all seem to be within the range of auditory perception of oscines. It is therefore hypothesized that parameters varying within species-specific limits have a potential for conveying a message about the species, and that parameters varying within these limits with the individual or the situation have an additional potential for conveying individual or behavioural messages, respectively. Blackbird song was also studied with respect to adaptations for acoustic communication. Selection has favoured the evolution of a functionally divalent signal, the motif parts being adapted for long-range communication and the twitter parts for short-range communication.