Primary feathers bend, twist, and sweep passively as velocity and attack angle change. This deformation may allow birds to maneuver during behaviors when most of their wing is experiencing deep stall. Our work suggests that these feathers increase spanwise flow and, thus, lateral (roll) stability. in addition to maintaining lift at high attack angles and minimizing the effects of turbulence by bending. This work has implications for the next generation of aircraft wings by enhancing control, increasing the critical stall angle, and increasing stability.