People in the town are blessed with the presence of a real, live angel, but it takes them no time at all to turn him into a sideshow attraction:
But when they went out into the courtyard with the first light of dawn, they found the whole neighborhood in front of the chicken coop having fun with the angel, without the slightest reverence, tossing him things to eat through the openings in the wire as if he weren't a supernatural creature but a circus animal. (4)
And things don't get better. When the little boy starts to visit the old man, "The angel was no less standoffish with him than with other mortals, but he tolerated the most ingenious infamies with the patience of a dog that had no illusions" (11).
And one last thing, which makes us think that captivity is actually a major deal. Pelayo's job? Bailiff. Bailiffs in modern U.S. courts have a variety of roles, but in the small town that Gárcia Márquez is writing out, they basically would have been jailors. That means that Pelayo's job is keeping people locked up. And what does he do once he quits his job? Builds a warren to raise rabbits.
Okay, so we've convinced you that captive animals are an important symbol. So, what does this symbol actually symbolize? Well, like everything in this story, it's complicated. It may suggest something about how the people in this town want to keep everything in little boxes. They lock the angel up because that's the only way they can make sense of out him.
Or, it may serve as a contrast to flight in general. The angel lands in Pelayo's courtyard because he somehow loses the power of flight, and he leaves as soon as he gets it back. And what's the opposite of flight?
Well, we think a cage is a pretty big contrast.