Paul Laurence Dunbar was an African American poet of the late 19th and early 20th centuries who lived through slavery, racism and segregation. So this poem is considered to be an extended metaphor where through out the entire poem Dunbar is comparing himself and all African Americans at that time with a caged bird that does not have the freedom to enjoy the nature and does not have the freedom to fly like all other birds meaning white people at that time.
The poet starts the poem with a sentence that is very direct and describes his feelings from the beginning which is "I know what the caged bird feels, alas", the word alas is an expression of the grief and sadness the poet is going through.
"When the sun is bright on the upland slopes, when the wind stirs soft through the springing grass" here the poet uses alliteration twice using the letters w and s.
"And the river flows like a stream of glass" the poet uses a figure of speech which is a simile to compare the river with glass, the purpose of this simile is to enhance the beauty of river stream by comparing it with glass that is to say that both are calm and clear.
"When the first bird sings and the first bud opes, and the faint perfume from its chalice steals" here Dunbar is describing the nature around the caged bird in more details by specifying the season as spring, which we realized from the birth of a new bird and the birth of flowers which are all signs of the beautiful season. A metaphor is also used here which is comparing the smell of the bud or flower with a chalice, a chalice is metal drinking cup that is used by Christians to serve wine in church, so that is to compare the soft and pale smell of the new flower with the metal cup.
Then he ends the verse by the repeat ion of "I Know what the caged bird feels" to emphasize on how they are both the same.
Then he starts to describe the physical battle the bird is going through after seeing the beautiful nature around him. "I know why the caged bird beats his wing, till its blood is red on the cruel bars, " here I believe that the poet is using sight imagery and a rather painful one by describing the bars of the cage covered with the bird's red blood, which is to describe the intensity of the struggle the bird is going through to be free.
"For he must fly back to his perch and cling, when he fain would be on the bough a-swing" here the poet is describing why he must get out. The bird must fly back to where he belongs to the tree branch and stick there, where he will be happy and pleased that he will start swinging on the branch.
"And a pain still throbs in the old, old scars, and they pulse again with a keener sting, I know why he beats his wing!" here the poet tells us that it was not the first time the he beat his wings against the bars in a very touching description, because there is pain that pounds in his old scares and every time they pulse again with a sharper and stronger sting. Which makes the bird remember how long he has been wanting and struggling to be free of his cage.
"I know why the caged bird sings, ah me," after the poet described for us how the bird feels from everything around him and why he beats his wings to get out and now he will tell us why the caged bird is still singing.
"When his wing is bruised and his bosom sore, When he beats his bars and he would be free" the poet uses another two alliterations here with the letters w and b, which he used to make the reader pay more attention to what the bird is going through and the fact his wing is bruised and his bosom or chest is sore of beating the bars.
"It is not a carol of joy or glee, but a prayer that he sends from his heart's deep core, but a plea, that upward to Heaven he flings I know why the caged bird sings". Here the poet is comparing between the normal bird of spring and the caged bird. The normal bird would usually be singing happily and enjoying the nature around him. A metaphor is used to describe the imprisoned bird which is comparing him with a human being that prays and unlike every other bird he does not sing he prays from his heart and requests for freedom and this metaphor is used to show how strongly the bird feels about wanting and needing his freedom.