Females occasionally create duets with males but they never sing solo-year-round singing behaviour in an Afrotropical songbird

Abstract

Our knowledge of birdsong mainly comes from studies focused on male songs produced in a short breeding period, even though we know that sedentary species sing year-round, female song is quite widespread and many species sing collectively creating duets and choruses. In this study we focused on daily and seasonal changes in singing activity of an endemic, sedentary, duetting, Afrotropical songbird—the Bangwa forest warbler. We collected soundscape recordings in six recording locations and used singing activity index to examine how vocal activity of males and females varies daily and seasonally and how it correlates with the rainfall. We found that Bangwa forest warblers sing year-round, yet they do it more in wet than in dry season. The rapid increase of singing activity occurs after first rain, at the beginning of the rainy season. Males sing significantly more than females. Females never sing solo, however, in 13% of songs they create duets by joining male solos. The pattern of daily singing activity is sex-specific and seasonally variable, with two peaks (dawn and dusk) observed in males and only one in females (dawn). In Bangwa forest warbler male singing behaviour is similar to that of many songbirds, suggesting that territory defence and female attraction as main functions of singing. Females, which create duets and never sing solo may use songs in mate guarding, signalling commitment, resource defence or intersex territory defence. Duets observed year-round may suggest cooperative resource defence. Results of the study show that examining year-round singing behaviour is crucial to fully understand the evolution and functions of male and female songs.