Possible meanings of "the rustling of wings" are 1) the boats that have sails are spoken of as having wings. AT: "Woe to those who live in the land beyond the rivers of Cush, whose many ships look like insects on the water" or 2) the rustling of wings refers to the noise of insects that have wings, perhaps locusts. (See: [[rc://en/ta/man/translate/figs-metaphor]])