Problem with broody hen behavior is they expect their chicks to eat off the ground themselves. Fledglings are mouth fed by their parents for a long time.
I would try to find a solution for your cat for a few days, and try to re-unite the fledgling with it's parent as the other members have described.
I would try to find a solution for your cat for a few days, and try to re-unite the fledgling with it's parent as the other members have described.