What are the poetic devices used in Maya Angelou's poem "Caged Bird"?

Maya Angelou uses a myriad of poetic devices in "Caged Bird," including metaphor, rhyme, imagery, alliteration, personification, and repetition.

In the poem, Angelou employs these poetic devices to contrast a free bird with a bird who is confined to a cage; the two different birds serve as metaphors for people free from oppression and people who are oppressed by society, respectively. Considering Angelou's personal history and the themes of her autobiographies, the caged bird, more explicitly, is a metaphor for African Americans who experienced racism and discrimination through slavery and Jim Crow laws in the U.S. Like the caged bird in the poem, African Americans were physically confined or restricted due to slavery and segregation, but they still vocally demanded their freedom.

In addition to using metaphor, Angelou utilizes repetition to reinforce the idea that African Americans cried out for freedom from oppression even in the bleakest of times when their oppressors did not want to "hear" them. Angelou repeats the third and fifth (final) stanzas, with the caged bird singing for freedom: 

The caged bird sings/with fearful trill/of things unknown/but longed for still/and his tune is heard/on the distant hill/for the caged bird/sings of freedom.

In the above quotation, note the end rhyme in the second, fourth, and sixth lines with "trill," "still," and "hill." We also find end rhyme as well as alliteration in the second stanza of the poem, when Angelou describes how the caged bird is physically confined. In the second stanza, the caged bird is in "his narrow cage" and "can seldom see through/his bars of rage" ("seldom see" forms the alliteration, while "cage" and "rage" form the end rhyme).

Finally, there is vivid imagery in the first stanza when the free bird "dips his wing/in the orange sun rays" and personification and alliteration in the fourth stanza when the caged bird's "shadow shouts on a nightmare scream." In this example from the fourth stanza, note the repetition of the consonant "s" and giving the caged bird's shadow the human quality of shouting, which emphasizes the bird's nightmarish existence living in confinement.