When you see (or hear)  this get ready.

This means there’s a good chance they will all scatter. It’s the warning.

The sound is like a long dry cough, not at all what you would expect.

Above you can see all the Spoonbill stopped feeding and are alert.

Of course like any group around food they can also ignore the one calling.

The morning I shot these I don’t think a single bird flew off after an alert. Guess I’m not that scary LOL.