The sound of the whistle... https://youtu.be/VfXE-RxKna4

I saw trained pigeons flying from my hotel rooftop in Wuhan when I visited in 2001. Someone on another building was commanding them to fly in patterns with flags. I don't recall if there were any whistles involved, but it was a really captivating sight to watch that I have never seen since.

This is another informative video, if you want to see the crafting process: https://www.dailymotion.com/video/x78adua

I thought for sure this was going to be whistle designed to scare off pigeons or something. Turns out they attach whistles to pigeons so they make sounds when they fly! Very interesting.

This sounds similar to the sound a hybrid Toyota makes when backing up. I wonder if in this geographic area, hybrid car awareness sounds should be something like construction banging, just to differentiate from the ambiance.