As environmental change continues and increases, understanding how species will respond to change and how these responses may affect populations will be important for conserving and managing species. Red-cockaded Woodpeckers (Picoides borealis) are well-studied and provide an ideal system in which to examine ecological and evolutionary questions related to life histories because monitoring them accurately is relatively easy, their behavior is well-described and structured. In this study, I examined the following questions using long-term data (1980-2013) from two study sites in North Carolina: 1) what traits contribute most to lifetime fitness, 2) how have traits changed over time and how is climate change influencing life history, and 3) to what extent are traits that contribute to fitness and that are changing over time heritable in this species. I found that a multitude of factors contribute to different aspects of fitness, including: parental age and hatch date affecting survival to year one and probability of attaining breeding status; and lay date, clutch size, age at first reproduction, and variance in clutch size affecting lifetime fitness. I also found that many traits were changing over time including lay date, clutch size, partial brood loss, and survival to year one. These traits were strongly influenced by local climate variables at each study site, but it is not clear that climate has changed over time at the study sites to account for all the observed changes in life history traits. Habitat improvement has also played a role as evidenced by increased fledgling production in terms of raw numbers (without accounting for covariates). I also found that lay date, clutch size, and partial brood loss had low heritabilities after accounting for other random and fixed effects. These results indicate that Red-cockaded Woodpeckers at these two study sites are shifting traits successfully in response to changing conditions, and that these changes are in the direction that increases aspects of fitness. These shifts indicate that individuals are plastic with respect to these traits, but most of the variance in traits was related to external habitat-associated factors rather than additive genetic variance or environmental × genotype interactions. / Ph. D.