Assessing song quality and its influence on mate attraction and fitness in European starlings

Bird song is an important sexually selected signal used for mate attraction. Among males, songs differ in their attractiveness to members of the opposite sex. The complexity of features of song may be an important way for a male to demonstrate his skill or experience and there are numerous studies showing that song characteristics are associated with the ability to attract a mate and with reproductive fitness. This dissertation identifies many different song features that may reflect male quality and investigates their importance in the European starling (Sturnus vulgaris) mating system.;In Chapter 3, the effect of song quality on paternity loss was assessed. Males with low variability in bout duration and sound density and high repertoire diversity were less likely to be cuckolded by other males, demonstrating that females may evaluate these song features in their social mates prior to seeking extra-pair mating opportunities. Cuckolded males were also found to fledge significantly fewer offspring than males that retained paternity in their broods.;Chapter 4 documents consistent temporal variation in primary and tertiary sex ratio allocation over four reproductive seasons in starlings, and explores possible causes for the bias. Starlings seemed to bias their sex allocation in response to climate patterns, producing more male offspring during the risky periods at the beginning and very end of the breeding season, and more female offspring during the more stable period in between.;Song is composed of many acoustic features which act together to make up the signal that females use to assess potential mates. In Chapter 2, I identify and measure a variety of acoustic features that may reveal important information about male quality and test their impact on mate attraction success and reproductive output. Males that sang bouts composed of a greater variety of syllables tightly packed together were more likely to attract mates than males that sang shorter bouts with lower syllable diversity and sound density. Males were also more successful if they produced a greater proportion of complex syllables requiring coordination of both sides of the syrinx or used pulse-tones or low frequency sounds.