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Abstract
This dissertation investigates how female zebra finches, who do not sing, respond to male courtship song. Chapter 1 argues that sexual selection research should integrate neural mechanisms of mate choice. Although male songbird courtship has been extensively characterized, female behavioral and neural responses remain poorly understood despite their importance for reproductive fitness and evolution. Chapter 2 analyzes the temporal structure of male zebra finch song and shows that these songs typically exhibit a hierarchical rhythmic structure that may shape how females perceive and evaluate songs. Chapter 3 shows that females are more behaviorally responsive than males to novel songs and rhythmic song-like stimuli, particularly in social settings, with response strength depending on spectral structure and familiarity. This suggests that females may be especially sensitive to the combination of particular song features and social context. Chapter 4 introduces a new preference assay and shows that females interacting with males under semi-natural, multimodal conditions typically express consistent and moderately repeatable transitive preferences. Females also exhibit context-dependence and individual variability, which may help explain inconsistent results in preference assays. Chapter 5 presents the first extracellular recordings from female HVC (a song control nucleus in males). Results demonstrate robust, heterogeneous, and class-selective auditory responses to conspecific songs as well as premotor activity preceding calls. These findings indicate that female HVC participates in complex perceptual processes as well as vocal production, challenging the view that it is merely vestigial. Chapter 6 shows that song system nuclei are embedded in broader associative and social networks, with major hub regions like NCL, located immediately ventral to HVC, providing anatomical context for how female HVC could interact with higher-order decision-making circuits. Chapter 7 argues for a revised view of the female song system, in which female HVC is a functional node in a distributed, socially oriented network that supports flexible, attention- and state-dependent integration of vocalizations, social context, and internal factors rather than simple detection of fixed preferences. Altogether, the results suggest that females primarily assess whether males express species-typical development, condition, and social competence, with individual variation in female behavior and neural adaptation helping to explain inconsistent laboratory preference measures. By complementing prior work on male song production with analyses of female behavioral and neural responses, this dissertation offers a more complete account of zebra finch courtship and supports an integrative understanding of how receivers shape evolution.