What is theme of the poem "Sympathy"?

Paul Laurence Dunbar was the son of former slaves. His
father had escaped enslavement by running away. By his mother, the oral tradition of
African-Americans was passed on to him. So, when he says “I know what the caged bird
feels," he actually knows it.

The agony of
the oppressed African-Americans is the most prominent theme of Dunbar's poem
“Sympathy.” It’s been expressed through the sufferings of a "caged bird."
"The caged bird" has got wings like a free bird, but it can’t use them to fly. Instead,
it uses its soft wings to strike against the iron bars hoping to break open the cage.
This leaves the poor bird bleeding with sore wings.

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…the caged bird beats his wing
Till its
blood is red on the cruel
bars; 

In this way, in a very
somber tone, the poet expresses the ordeal of African-Americans. Down the ages, they
have been oppressed and enslaved by the whites. The iron bars of racism have prevented
them to live a normal life.

Besides, longing
for freedom is another important theme running through the poem. The
nature in its beautiful forms makes the bird all the more desirous to come out of its
cage and fly boundlessly. But, imprisoned and helpless, it can feel the nature only
through its sound, sight and smell:  

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    When the sun is bright on the upland slopes;
  
When the wind stirs soft through the springing grass,   
And the
river flows like a stream of glass;
    When the first bird sings and the
first bud opes,   
And the faint perfume from its chalice
steals—

With the hope that
“he would be free,” it beats the iron bars endlessly and prays to the Heaven to end its
suffering and liberate it.

Another important
theme that cannot be overlooked is that of hope against all odds. Instead
of merely waiting for its prayers to be answered or any help to arrive, it continuously
strikes against the iron bars with its wings. It stops only when its wings begin to
bleed, and, after some time, it restarts again. It never gives up.
 

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!

The blacks, too, have
continued their struggle for freedom with this same indomitable spirit through
centuries. They won’t stop until they find it.

So, we see
that “Sympathy” is about the anguish and pain of the downtrodden African-Americans; it’s
about the evil of racism; it’s also about hope and faith, and, about the invincible
spirit of the oppressed to persist and carry on.