"Caged Bird" uses multiple poetic devices to convey and enhance its meaning. I've only listed three of them here, but a close reading of the poem yields many more, so it would be a good idea to consult the eNotes Guide to Literary Terms while working through the poem to see which poetic devices you can identify. Metaphor, alliteration, stanza, verse, and mood are all present within the poem.
Three devices I noticed include:
An allegory is
an extended metaphor in which characters, events, settings, objects, etc. have symbolic as well as literal meanings.
The contrast between the lives of the caged bird and the free bird is an allegory for the contrast between the lives of African Americans and their white counterparts. The caged bird is trapped in a small space, tied down and mutilated (with his clipped wings) to prevent him from ever leaving. He dreams of the freedom that the free bird takes for granted.
Anthropomorphism is when human characteristics are given to animals, objects, or gods.
"Caged Bird" anthropomorphizes both the caged bird and the free bird, describing them both with human thoughts and emotions. This poetic device enhances the allegory Maya Angelou has created. The caged bird, like the African American community, "long[s] for" freedom from the confines in which he is forced to live, while the free bird, like the white community, "names the sky his own" and assumes that his freedom is the natural state of things.
The entire poem is written in rhyme, which
serves as an element of rhythm emphasizing the beat [of the poem].
Rhyme can be used to make relationships between the rhyming words themselves, so it is worth examining where the rhymes occur within the poem. For instance:
But a bird that stalks
down his narrow cage
can seldom see through
his bars of rage
The relationship here is between "cage" and "rage"—the cage is constructed of "bars of rage" from which the bird cannot escape and through which he can "seldom see" the outside world. Likewise:
The free bird thinks of another breeze
and the trade winds soft through the sighing trees
and the fat worms waiting on a dawn bright lawn
and he names the sky his own
The relationship between "breeze"/"trees" vividly evokes the sense of the outdoors, a bird's natural habitat, while the half-rhyme of "lawn"/"own" implies that the free bird feels that the breeze, the trees, the lawn, and everything else all belong to him by rights.
You may need to read the poem multiple times to pick out the various poetic devices Angelou has employed within it, but as you can hopefully see from the examples above, there are plenty of devices to choose from.