A Heron usually feeds at dawn and/or sunset. In populated areas it is usually at dawn when there is a minimum of human activity. It has to be shallow water for a raccoon to take a fish, I don't know about mink or nutria. Check on Google as to eating habits. Also, a Heron will not keep any feeding pattern. He may be back tomorrow or he may never return, but a different heron may. They will fly several miles from their nesting area in search of food for their young. This season's young have probably fledged by now and are feeding on their own near their hatching grounds. They will gradually enlarge their search area as they grow older, much as any predatory bird.