Natural and anthropogenic disturbances affect the abundance, availability, and distribution of resources within oak savanna, an early successional ecosystem. Disturbance-dependent species, such as cavity-nesting birds of the oak savanna, are experiencing population declines. The cavity-nesting bird guild depends on snags (standing dead trees), which occur naturally, but are also formed as a result of oak savanna restoration practices. In order to understand the role that snag density plays on the ecology and behavior of cavity-nesting birds, we assessed the relative abundance, evidence of reproductive success, activity budgets and substrate use of the guild in five oak savanna sites. We also analyzed the influence of other site characteristics including canopy cover and area on all bird relative abundance, diversity, and cavity-nesting bird behavior. Cavity-nesting bird and all bird abundance were related to snag density by polynomial functions where the relative abundance of birds was highest at either ends of the snag density range. The site without any confirmed nests and the lowest species diversity had the lowest snag density (5.4 snags/ha) and the most homogenous canopy, however, the weight of juvenile Eastern Bluebirds was highest at that site. No differences in activity budgets were found between sites at the guild scale, however, substrate use at the guild and species scale was different between sites. At the guild scale, as snag density increased, snags were used more often and as canopy cover increased, snags and dead wood were used less and live wood was used more often. At the species scale, patterns of substrate use were similar to those of the guild, however, the site with the lowest snag density and homogenous canopy particularly influenced substrate use as canopy cover increased. These results suggest that not only is snag density important to cavity-nesting bird ecology and behavior, but that the vegetative structural context of snags in oak savanna is an important factor as well and should be considered when oak savanna restoration takes place.