Examining repertoire size and seasonal variation in male song and temporal variation in various behaviours in the Purple sunbird (Cinnyris asiaticus)

Abstract

Birds are some of the most acoustically active animals on Earth. Many studies trying to understand and decipher their vocal communication have been published over the years. Song is one of the widely studied vocalisations by ornithologists. Attempts to understand the song began with informal field notes describing their attributes as perceived by human ear. With advancement in science, newer and more robust methods of quantification opened a plethora of questions that can be asked about the song. From an evolutionary perspective, many studies provide evidence that song functions as sexual display in many birds. This thesis attempts to explore the similar theme in a highly abundant species of sunbird in the Indian subcontinent, the Purple sunbird (Cinnyris asiaticus). It is a small passerine with a characteristic long-curved bill. Very few studies have tried to explore the structural aspects of the song in this species. This thesis looks at both note structure and phrase structure of the song in both breeding and non-breeding season. Such a comparative account has provided evidence in the changes that occur between the seasons highlighting season specific characters. Many birds are known to utilise multimodal sexual displays. Thus, to identify any such behaviour in this species, a behavioural study was also conducted in the non-breeding season. An overall time-activity budget analysis showed that the bird displaces from one position to another the most, which agrees with the dynamic nature of this bird. It was found that the male is usually stationary during the song bout and performs body movements at the perching position. On comparing this data with a similar study in breeding season can yield more insight into whether visual mode aids in sexual display in this sunbird species.