Question
I have a koi pond in Western Pennsylvania, Pittsburgh, netted to prevent blue heron from taking the fish.  Must I keep the netting on all year to prevent the heron from fishing?  Or do they have a hunting season?

Answer
They hunt all year round.  Their eating habits are dictated by their migratory habits.  This year some birds' migration patterns have shifted, leaving their expected routed almost incalculable.  So, this year it is tougher than ever to predict when they will leave your area.  You should probably leave the netting on all year.