There are a pair of finches who buid a nest on top of a decorative column on my porch every spring [View all]

It's protected by an overhanging roof. I leave it there as I don't think they do any harm. Only so far this year it has been attacked and torn apart by the cow birds 3 times. Yet after every attack the finches rebuild it back in the same place.

I don't know if I should put a blocker up there to make them have to find a hopefully safer spot to build, or just leave nature to take care of itself?