social species, dominance rank has implications for an individual’s health and fitness. Dominant individuals often receive greater access to resources, protection from predators, higher quality territories, and increased reproductive success. Because of these advantages, dominance rank could affect physiological systems such as immunity. In this thesis, I discuss two studies that examine the relationship between social dominance and innate immune function using black-­‐ capped chickadees (Poecile atricapillus). In the field, we found that in males, a high dominance score was correlated with low immune function in the fall. In captivity, we gave an immune challenge in the form of a lipolysaccharide (LPS) injection to the top-­‐ranked individual in each flock and observed changes in dominance behavior. LPS provided a significant energetic cost but did not alter dominance behavior. These results indicate a potential trade-­‐off between dominance and immunity, and shows that a short-­‐term illness may not negatively affect rank.