| The nestling period of altricial birds is a time of rapid body growth and development, yet there is a paucity of published studies examining the ontogeny of immune function and the impact of environmental perturbations, such as food restriction, during this time. The first study of this thesis examined the ontogeny of specific adaptive immune response in altricial zebra finches Taeniopygia guttata, using repeated vaccinations with keyhole limpet hemocyanin (KLH) antigen. We found that capacity for adaptive antibody response developed after the first week post-hatch and that strength of response significantly increased throughout the nestling period. However, secondary antibody response level was significantly lower than adults prior to fledging. The second study in this thesis examined developmental patterns of constitutive innate and adaptive immune indices in house sparrows Passer domesticus. Lysozyme activity significantly decreased with age, likely representing catabolism of maternal lysozyme from the egg albumen. Levels of circulating adaptive IgY, as well as innate agglutination and lysis, increased throughout the nestling period, yet at fledging were significantly below levels found in fully-grown birds. There were no significant differences between juvenile birds and adults in these measures, indicating that full maturation occurs early post-fledging. The final two studies examined the long-term and acute impacts of food restriction on immune function. The third study examined the effects of compensatory growth on development of adaptive antibody response in zebra finches. Compensatory body mass growth was observed following food restriction yet, while reductions in tissue maturity were observed, adaptive antibody response to KLH was not altered post-restriction. In the final study of this thesis, we imposed food restriction on house sparrow nestlings and measured multiple indices of immune function and growth. During food restriction, levels of the acute phase protein haptoglobin were reduced compared with controls, yet complement-mediated lysis and circulating IgY antibody levels did not significantly differ between treatments. Food restriction resulted in significant reductions in alimentary organ, heart, and flight muscle masses. These studies show that immune function is immature near fledging age and that food restriction does not significantly alter immune function in growing birds. |
