As the feathers of the parrot are green and help it to better imitate the spring, the color of the workers is black, which help them to be slaves.

I think the workers imply that they do not have the luxury of tranquility or time to practice the "required" articulation of "R" even if them being not able to pronounce it properly means their execution!

This shows how they work on getting self-healed quickly, so they can continue their work, and also El General never knows that they are being harmed.

And they wait for the rain to cry and scream to make it hard for El General to distinguish between their tears and the rain. Because if El General notices their screaming and crying, he will think they are weak and angry.

This implies that the Haitian people, desperately, consider El General to be the most powerful and strong creature in the whole world.

There is a kind of hope here that, eventually, they get to destroy their source of suffering.

I think that the Haitian people are miserable and depressed to the extent at which they believe that cane grows just to deliberately make them suffer.

I think the parrot here is symbolizing El General himself. Parrot is not spring which brings joy and happiness. El General is a bad person, however, he is pretending to bring his people joy and justice from his palace.

We can also think of the parrot at the cage as a symbol for the Haitian people who were considered slaves. Even though the parrot is not free and is caged, it is still imitating spring, by the same token, in spite of the oppression and injustice, the Haitian people are not only pretending that everything is ok, but rather that they are happy! Because being miserable may actually upset El General.