Thanks you, the article doesn't have the sound.

Nor does it have a photo of the whistle attached to a pigeon!!!

Isn't the leftmost pigeon carrying one here? http://www.chinatoday.com.cn/ctenglish/2018/cs/201911/W02019...

I guess it is, but it wasn’t clear to me before seeing other images.

Gotta be a sign of the times that the first spontaneous association I had was that of air raid sirens.

Thanks a lot for the link though!

That's kind of horrific. Not only is there a horrible sound, but then the camera shows the results of this aerial attack with all of the bird poop. Such a strange video.

You don't like Beijing's version of the whistle tip?

Sounds just like a lot of electric car's low speed sounds