The unique singing behaviour of an African lark : song variation in the Monotonous Lark Mirafra passerina

Abstract: Bird song can teach us much about animal behaviour and evolution. This study presents a type of song variation that has yet to be extensively studied. The Monotonous Lark Mirafra passerina is a nomadic lark with an iconic, simple and repetitive song. It has been noted to have a large song variation between irruptions, but limited variation in the same irruption, a behaviour previously, to my knowledge, unknown in the avian world. This study aims to describe the song and analyse the variation within and between irruptions, and try to explain the underlying mechanisms behind the variation. This article studies the song by analysing song material spanning 30 years with 140 samples, most from South Africa. The whole song and the syllables were measured. A custom edit distance and Euclidean distance were used to quantify song differences. Principal component analysis was performed on both syllable measurements and the whole song. The results showed a larger song variation between irruptions compared to within irruptions. It also showed that the song varies greatly between irruptions; however, a general pattern of how the song is structured was found. In addition, some indications of song retention between years were noticed. This study describes a unique example of avian behaviour that can broaden our knowledge of animal communication and its evolution and development.