Date of Award

10-5-2017

Degree Type

Thesis

Degree Name

M.Sc.

Department

Biological Sciences

First Advisor

Mennill, Daniel

Second Advisor

Norris, Ryan

Keywords

Kent island, male-male vocal interactions, Predictor of attack, Savannah Sparrow, Seasonal variation of singing activity, Soft song

Abstract

In this thesis, I examine the function of acoustic signals in Savannah Sparrows, Passerculus)sandwichensis, by analyzing temporal variation in vocal activity, and by conducting a playback experiment. In my first data chapter, I analyze longUterm acoustic recordings to study diel and seasonal variation in vocal activity of Savannah Sparrows. I show that singing activity of male Savannah Sparrows varies with time of day, time of year, and breeding stage. Males exhibit the highest level of song output in May, upon arrival on the breeding grounds, and the lowest level in August, before departure from the breeding grounds. Song output peaks in the early morning, consistent with dawn chorus behaviour, but this pattern is common only prior to pairing; after pairing the dawn chorus is reduced and male song output peaks in the evening, consistent with dusk chorus behaviour. These patterns suggest that dawn choruses serve a territorial function whereas dusk choruses serve a femaleUrelated function in Savannah Sparrows. In my second data chapter, I present the results of a playback experiment designed to test whether Savannah Sparrows signal their intention to attack a rival male. I simulated an intruder using song playback and a taxidermic model, and explored which behaviors were associated with physical attack. Savannah Sparrows produce soft songs and chip calls at significantly higher levels before attacking rivals, whereas three other measured behaviors (aggressive calls, wing waving, and passes over the model) do not predict attack. My research advances the field of animal communication and provides a foundation for future research on signal function and social interactions involving vocal signals.

Available for download on Wednesday, October 17, 2018

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