A great article, and photographs, from Ellen Jennings.
Great Blue Heron parents take turns at the nest, the adult that leaves the nest feeds himself and sometimes brings food back for the chicks. In this exchange of duties the adult and chicks on the nest were well aware that the other parent was coming in as he first landed in a tree to the left.
The incoming adult then walked down some branches and pushed his way onto the nest; there is not a lot of room.
The adults stood together for several minutes, some kind of Heron communication going on.
Then number two was off, taking the reverse path up the branch then disappearing towards the river.
After (s)he was gone the remaining adult assumed the watch, the chicks squawked a bit, then they settled down.
Click on any photo for larger view.