Doctor of Philosophy
Birdsong is a complex, learned vocalization that is a phenotypic expression of male quality. The developmental stress hypothesis describes how the cost to possessing a high quality song is paid in early development. Stressful early-life experiences have adverse effects on the development of the neural circuitry that regulates song learning and production, which results in a male advertising with a low quality song in adulthood. The purpose of this thesis was to test the developmental stress hypothesis in several respects in European starlings (Sturnus vulgaris). My objectives were to assess the long-term effects of developmental stress on (1) physiological and cognitive-behavioural traits indicative of phenotypic quality in adulthood (Chapters 2, 3), (2) female songbirds’ auditory abilities and response to song (Chapter 4), and (3) male songbirds’ song behaviour and brain development across the lifespan in a species capable of learning new songs throughout adulthood (i.e., open-ended learner; Chapter 5). Juvenile starlings were reared in one of two developmental treatment conditions: control, or unpredictable access to food. The developmental treatment induced similar physiological effects in both sexes. Relative to controls, treatment birds had less fat during the developmental treatment, but following the treatment gained a significant amount of lean mass. In adulthood, aspects of endocrine regulation were also affected. Conversely, the effects on cognitive function differed between the sexes. Females reared in the treatment group were slower to acquire an auditory learning discrimination, while this effect was not observed in males. Treatment females were also less inclined to listen to conspecific (versus heterospecific) song in a behavioural choice paradigm. Furthermore, this behavioural response was mirrored by less neural activation in auditory forebrain regions when listening to conspecific song. Lastly, the developmental treatment did adversely affect male song production and the supporting neural structures, but the effects diminished with age. Songbirds that are open-ended learners, compared to closed-ended learners (i.e., do not learn new songs in adulthood), may have a pattern of neural plasticity that allows for greater recovery from the effects of developmental stress. These results support the hypothesis and highlight the importance of sex and species differences.
Farrell, Tara M., "Developmental Stress and the Effects on Physiological and Cognitive-Behavioural Traits in European Starlings" (2015). Electronic Thesis and Dissertation Repository. 3348.