The symbol of the cage is used throughout the famous poem "Caged Bird" by Maya Angelou to develop the themes of oppression and lack of freedom.
When a bird is free he flies at his leisure and he feels empowered and brave to even "claim the sky" and name it "his own," and he has dreams, attainable dreams, "of fat worms" and "another breeze." But when a bird is constrained to a cage, when his dreams and his hopes, his wings and his feet, have been literally and metaphorically cut short, when his freedom has been taken from him, he sings of freedom, but also of uncertainty, but his is a trill full of fear. A caged bird is so frightened that even his shadow "shouts on a nightmare scream."
Throughout her work, Maya Angelou resorted to the symbol of the caged bird as an allegory of the African American that had been forcibly chained, oppressed, and slaved.