Females sing more often and at higher frequencies than males in Australian magpies

Abstract

Birdsong is a particularly useful model for animal communication studies. However, current knowledge is derived mainly from the study of male song, and is therefore incomplete. Here, we investigated whether singing behaviour differs between sexes in the cooperatively breeding Western Australian magpie (Gymnorhina tibicen dorsalis). This subspecies lives in territorial groups, and in our population there is a female-biased sex ratio, which may lead to a high level of female-female competition for males. Observations of 94 magpies (54 females, 40 males) revealed that females sang more often than males. As bird song is a sexually multidimensional signal, we also studied amplitude and structure of the main territorial high-amplitude song in magpie; the carol. We found that females sing at the same amplitude as males, but that male and female carols exhibit differences in frequency. These results highlight the importance of studying female song and may change our perception regarding the evolution of sex-specific traits, given the primary focus on male singing as a sexually selected trait in the literature to date. The next step is to discover additional species in which females sing more than males in order to improve our currently incomplete understanding of the evolution of bird song.