How would you explain this sentence?
We cut him free of his bindings then turned northwest toward the circle. Our boots impacted softly against the dust, which settled like lime on the legs of our pants. Birds and shadows were caught quickly by our eyes, then returned to a fluttering periphery of hollow noises: a motor in the distance, an old man breathing from a doorway, the tails of his wife’s robes softly dragging across a mud floor. We moved until over the crest of a low rise we saw lights splayed out in all directions.
How would you explain this sentence: Birds and shadows were caught quickly by our eyes, then returned to a fluttering periphery of hollow noises? Does the shadows refer to the shadows of the birds? Who returned to a fluttering periphery of hollow noises? How would you explain “fluttering” in “a fluttering periphery of hollow noises”?
Thanks!