At Victoria Point on Sunday, the tide was out and I watched an interesting interaction between two bird species. One of them was a white-faced heron (Egretta novaehollandiae) that had been foraging on the mudflats for quite some time already. It was eventually joined by a little egret (Egretta garzetta). As you can tell from the genus of both species, they are closely related - essentially, you could call the heron a grey egret, and the egret a white heron if you wanted to. The egret began to forage by trailing the heron quite closely. Graham Pizzey in his excellent field guide notes that this behaviour by the egret allows it to capture prey items escaping unnoticed by the other bird. There was a certain invisible ring of comfort/discomfort around the heron, however, and whenever the egret crossed that barrier, the heron would become visibly bothered and rebuke the space invader (see the photo at the top of this page also). Af...