The structure, context and possible functions of solos, duets and choruses in the subdesert mesite (Monias benschi)

Subdesert mesites produced five distinct types of vocal element which they combined to produce two broad classes of song 'syllable'. One of these syllables was exclusive to males and the other was mainly given by females. Song syllables were either produced in series by single individuals to give solo songs, or 2-5 five birds vocalised simultaneously with varying degrees of temporal precision to give duets and choruses. Pair-duets were the most common and male solos the least common form of song recorded. Females initiated and terminated significantly more songs than males and male syllables followed female syllables more promptly than the converse. However, the syllable structure of male and female solos changed when synchronised to form pair-duets indicating that, in contrast to most previous studies of duetting species, these songs are a function of both male and female behaviour. Only a subset of each group contributed to duets and choruses and participation was positively correlated with mass for males and females both within and across groups. Song activity remained at a low but relatively constant rate throughout both the day and season. The wide variety of contexts in which songs were produced indicated that they serve multiple functions: some appear to be cooperative endeavours (e.g. Io maintain contact in dense vegetation and to defend territories), others may be underpinned by conflicts and could function in mate-defence or in inter- and intra-sexual assessment within groups.