Which figure of speech is used in this text?
I am a feather on the bright sky
I am the blue horse that runs in the plain
I am the fish that rolls, shining, in the water
I am the shadow that follows a child
—N. Scott Momaday, "The Delight Song of Tsoai-talee"

 - understatement
 - anaphora
The text uses anaphora, the repetition of the same word or words at the beginning of several phrases or clauses.
Momaday repeats the words I am at the beginning of each line.