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NESTLINGS AND NEURONS: EARLY LEARNING, AUDITORY PERCEPTION, AND SIGNAL EVOLUTION IN SONGBIRDS

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Abstract
Social decisions of animals are guided by innate predispositions, sensory biases, and experiences related to communication signals. In many taxa, early life experiences are especially formative in later signal discrimination, signal production, and mate preference. Missing from our understanding is how sensory circuits are innately primed, then shaped by experiences to ultimately result in behavioral decisions. My dissertation addresses this gap by seeking evidence for natal learning and population-specific sexual signal structure in songbirds. I first experimentally exposed wild nestling swamp sparrows to songs from either their local subspecies or a foreign subspecies. I found that only nestlings that heard both local and foreign song types were able to discriminate between the two. With nestling learning ability tenable in the wild, I then performed electrophysiological recordings in the auditory forebrain of zebra finches across ages and showed that auditory processing is already adultlike and able to distinguish species song types within the first 10 days. I next explored how auditory forebrain responses change in concordance with early social and auditory experiences by raising zebra finches in different social environments. Units from cross-fostered and isolated individuals showed increased firing rates and decreased selectivity and responsiveness relative to normally-reared units. Specifically, cross-fostered units were less selective and responsive to conspecific song, mirroring an observed reduction in attentiveness to conspecific songs during behavioral trials. These first three experiments, in combination, establish evidence of neural plasticity and song type learning ability in young altricial songbird nestlings, and fill in some of the steps linking sensory experience to behavioral output. My last project returned to wild swamp sparrows to explore the effect of subspecies differences in beak morphology on fine scale song structure. I show that songs of the larger-beaked subspecies contain more low-performance notes and note transitions than the smaller-beaked subspecies, and that consistency of a given acoustic metric was highest for features that each subspecies sang with lower performance. Taken together, my dissertation broadly connects signalers with receiver behaviors through signal production and sensory processing, as well as suggests implications of these processes in the context of population divergence in swamp sparrows.
Type
Dissertation (Open Access)
Date
2024-05
Publisher
License
Attribution 4.0 International
License
http://creativecommons.org/licenses/by/4.0/
Research Projects
Organizational Units
Journal Issue
Embargo Lift Date
2024-11-17
Publisher Version
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