Understanding how flight capacity increases in extant birds throughout ontogeny can provide crucial insight into the evolutionary transitions of flight. Using this approach, Wing-Assisted Incline Running was proposed as an evolutionary model after studying the development of flight capacity in Chukars, a precocial bird that flaps to run up steep inclines for refuge. In Chukars, flight capacity increases ontogenetically as locomotor investment shifts from hindlimbs to forelimbs. In the wing, increases in lift production and an adult flight stroke are facilitated as joints ossify and become more kinematically restricted. However, the structure of these developing joints and their relation to functional transitions in flight capacity remains unknown. We thus sampled Chukars at various age points to investigate these joints throughout ontogeny, focusing on the trabecular bone in the epiphyses. Trabecular matrix has been shown to structurally adapt to an organism’s function throughout ontogeny with high sensitivity, providing functional signals that correlate with behavior at various developmental stages. We collected microCT scans of 3 humeri and femurs at 6 age points (2dph-adulthood). As ossification increased across age, we were able to separate between developmentally and functionally relevant trabecular bone. Preliminary results show a functional signal with a notable shift near the age flight capacity becomes adult-like. Ongoing work continues to explore functional signals in the humeral matrix as well as in the proximal femur. This approach provides a better understanding of the ontogenetic functional morphology of flight and deeper insight into the roles of developmental processes and hindlimb-forelimb tradeoffs over flight acquisition in birds- both ontogenetically and evolutionarily.