I usually see this behavior referred to as “mobbing.”

It is often used to locate these birds of prey, who try their best to stay hidden. For wildlife researchers and photographers, it’s almost like having a camera network all over the outdoors to alert them when these animals get spotted. It also brings out the other rare birds as well.

The behavior itself is very unique in the animal world as it demonstrates cooperation between different species.

Mobbing isn’t considered an attempt to hurt or kill the target of the swarm, because an actual fight wouldn’t benefit either side, as birds are very delicate generally, so any small injury could mean the end for any of them. It’s mainly just to move them along so they don’t have an opportunity to snatch anyone up.