Electronic Thesis and Dissertation Repository


Doctor of Philosophy




Scott MacDougall-Shackleton


Developmentally plastic organisms can respond to stressful environmental conditions by altering multiple aspects of their phenotype, often in a permanent fashion. The timing of developmental stress influences these phenotypic alterations because the prioritization of resources to traits necessary to overcome the stressor may be costly for the development of other traits. Despite the importance of this timing, few studies in birds have accounted for it, and those that have usually examined the effect on a single or few variables. This dissertation addresses the outstanding issues regarding i) the effects of timing of developmental stress on developmental plasticity, and ii) the extent to which poor nutritional conditions, as opposed to changes in nutritional conditions, drive phenotypic plasticity. Using zebra finches (Taeniopygia guttata) as my study species, I manipulated food accessibility during early and or juvenile development (i.e. before and after nutritional independence) and measured various physiological and cognitive-behavioral traits. Results indicated that timing of stress significantly affected many (but not all) aspects of phenotype measured, including growth rates, body composition, immune function, associative learning, spatial memory, and endocrine function. In particular, nutritional stress during the juvenile period appeared to have strong programming effects on phenotype. Nevertheless, individual differences and sex differences in developmental plasticity greatly moderated the influence that timing of stress had on phenotypic development.