A comparative exploration of song structure and function between the sexes in the grey fantail (Rhipidura albiscapa)

Abstract

Avian communication systems have been considered model systems for vocal behaviour for many years, and as such have been studied extensively. However, historical research bias has led to an abundance of research on male vocal behaviour and much less focus on female vocalizations. Reflecting newer views that song is common and likely ancestral in females as well as males, birdsong research is shifting away from male-centric song definitions and functionality and exploring song in new ways. In this thesis, I aim to answer questions regarding the functions and evolutionary benefits of vocal behaviour using sound recordings and playback studies of a banded population of grey fantails (Rhipidura albiscapa). In answering these questions, my goal is to provide an evolutionary context to the functions of song in both sexes, rather than simply as a male ornament, and provide foundational data to ask further questions about why females sing in the grey fantail. There is currently no literature regarding how female or male grey fantails use song, despite their proclivity to communicate in all seasons. As such, I have posed hypotheses framed to answer questions about when songs are used during a breeding season, how males and females use songs differently, and whether songs and calls are referential and/ or dependent on contexts. I use both recordings from a natural context as well as experimentally induced vocalizations to test these hypotheses. I begin with a quantitative description of song in the species and compare female and male song. Next, I examine the ecological contexts of song use by dividing a breeding attempt into stages (nest-building, laying, incubation, chick rearing, and fledgling rearing) and exploring when song rates of females and males peak. I follow with two experimental studies testing territorial functions of female and male song, and testing for referential signalling in the presence of nest predators. I find that female and male grey fantails have the same song types, but their song rates, use of song during breeding, proclivity to vocalize during territory defense, and vocal behaviour in response to predators differ markedly. I find no evidence for referential songs or calls in grey fantails.

Date of Award	2022
Original language	English