How does the poet describe the world of nature?

“Caged Bird” uses rich nature imagery to evoke the contrast between the caged and free birds. The caged bird can barely sense the natural world outside the cage but retains hope that it will once fly outside in that world. The free bird not only inhabits that world but thinks and feels its possibilities and effects.
The free bird stanzas feature the sky and the earth as the full environment open to the bird. The celestial features of wind and sun are paired with the terrestrial ones of trees, worms, and grass. The sky belongs to the bird: “he names the sky his own.” The wind and breeze, in particular, are shown in several ways: glossed as a stream on which the bird floats, a breeze, and the trade winds making the trees sigh. The worms in the lawn are presented as part of the bird’s thoughts and anticipation.
The caged bird can barely see outside the cage, and it “sings of things unknown but longed for.” The “distant hill” is mentioned twice but not described except as distant. Although dreams are mentioned, they are made concrete only as a “graveyard” –part of the human-made rather than natural world—and contrasted to the “dawn bright lawn” of the free bird’s world.
Thus, Angelou uses imagery of the natural world to convey ideas about hope and its limits.
https://www.poetryfoundation.org/poems/48989/caged-bird

In “Caged Bird” by Maya Angelou, the speaker contrasts a free bird with one that is raised in captivity.
Nature is described in association with the free bird. In the first stanza, the speaker says that the free bird “leaps on the back of the wind” and “dips his wing in the orange sun rays,” daring to “claim the sky.” The buoyant tone of this stanza indicates that the bird is happy and that nature is his to conquer.
Nature is addressed again in the fourth stanza. The description is very similar to the first stanza, insomuch that the free bird “names the sky his own.” The speaker depicts the sky as a boundless expanse in which the bird is the master traveler.
In each of these stanzas, then, nature represents independence, hope, and possibility, in addition to the freedom it allows the bird to experience.