Looking Daggers

A pair of green heron were sitting quite amicably in this dead tree, not even bothered by nearby blackbirds. They looked around now and then as other birds flew overhead and sometimes gave out a squawk. 

Then, for some unknown reason they suddenly turned, pointing their long sharp beaks towards one another and stared each other down.

I thought they were siblings, but maybe rivals. Probably the same ones I saw last week.