A bird mystery.

Has anyone else heard of a Heron’s Parliament? I have known this phrase for as long as I have been interested in birds. Moreover I have been lucky enough to see one.
In the middle of a field a couple of miles from home there were about 20 Herons standing in a perfect circle all facing the central point.
I am not sure what they discuss although I might guess now that they would pass a Resolution asking the Government to restrict the number of Small White Egrets being allowed into the country.

The mystery is that I can find no reference to Heron’s Parliament in Google or in Wikipedia.

Has anyone else seen this interesting behaviour?