Please explain the symbolism found in the following quote from The Bean Trees: "He told me that the national symbol of the Indian people in Guatemala was the quetzal, a beautiful green bird with a long, long tail. I told him I had seen military macaws at the zoo, and wondered if the quetzal was anything like those. He said no. If you tried to keep this bird in a cage, it died."
In order to best understand the quote that you have given us, you need to think about the overall themes of this work and about the passage that comes just before the part that you quote.
First of all, let us look at the themes of the novel. As the eNotes discussion of the themes (link below) says, one of the themes of the novel is human rights which
... involve personal safety and freedom, which most United States citizens take for granted.
The passage you cite is making this point.
Before the part you quote, Esteban asks Taylor if the national symbol of the US is an alligator since so many people wear it on their shirts. This is a reference to materialism since this book was written in the '80s when Izod shirts with their alligator logo were very popular.
By contrast, Esteban says, the Indians of Guatemala had as their symbol a bird that dies in captivity. This is symbolizing their fierce desire to be free. This desire for freedom and human rights is why Esteban and Esperanza -- whose name means "hope" -- are in America in the first place.
So the discussion of the alligator and the quetzal is meant to symbolize the differences between complacent Americans who have their rights and care only about material goods and the oppressed, like the Indians in Guatemala, who value freedom so highly that they die without it.