As rapid climate change introduces novel environmental conditions, understanding how species vary in their response to change is urgent. Animal personality, behavior consistent within and variable among individuals, influences how populations adapt and respond to new challenges. Our research program focuses on interactions between Black-capped (Poecile atricapillus) and Carolina (P. carolinensis) chickadees across a northward-moving hybrid zone in southeastern Pennsylvania. We investigated nest defense behaviors as a proxy for boldness, a component of personality associated with an individual’s willingness to interact with a perceived threat. We simulated predation threats at nests in pure and mixed populations with a motorized decoy. Video analysis yielded measures of pair responses for three categories of boldness behaviors: approach latency, vocalization, and proximity to the decoy. All behaviors were moderately repeatable, as is typical for behavioral phenotypes. We modeled each behavior using linear and generalized-linear mixed methods. Preliminary analyses suggest the odds of observing a slow approach from Carolina or hybrid pairs were respectively over triple and nearly double the odds of observing a slow approach from Black-capped pairs. Carolina pairs expressed more alarm (mean 3.7 dee notes) in their calls than Black-capped pairs. Black-capped pairs remained close to the decoy more often than Carolina and hybrid pairs. Based on current models, we conclude that Black-capped chickadee pairs are bolder than Carolinas, with hybrids generally intermediate or more Carolina-like. These results indicate the importance of considering personality variation as ranges shift and foster new or greater contact between potential mates and/or competitors.