The Present and Correct blog had a brief post on pigeon whistles, “a small musical instrument that is attached to the tail of the pigeon so that it produces a sound when it flies.” I read the linked article about the history (very cool) but what on earth would that sound like?
The modern internet is mostly a hellscape BUT you know you can find an example of just about anything… including the sound of pigeon whistles on a flock of birds.