Answer:
Restricted movement
Explanation:
In the poem Sympathy by Paul Laurence Dunbar, the image of a bird in a cage suggest restricted freedom.
The caged bird has wings to fly just like every other bird but it couldn't because its movement has been restricted.
Sympathy is a poem by Paul Laurence Dunbar
I know what the caged bird feels, alas!
 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—
I know what the caged bird feels!
I know why the caged bird beats his wing
 Till its blood is red on the cruel bars; 
For he must fly back to his perch and cling 
When he fain would be on the bough a-swing;
 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!
I know why the caged bird sings, ah me,
 When his wing is bruised and his bosom sore,—
When he beats his bars and he would be free;
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!