MYSTERY SOLVED!!!

Every morning I would find the bird bath tipped over. I had found an inexpensive one so it wasn't very sturdy. But certainly sturdy enough for a robin or a blue Jay..
I thought it must be those pesky squirrels or maybe a cat trying to jump into it
So I broke down and got a concrete one. Weighs a ton and it would take a really big animal to tip it.

But tonight just before dark I saw who it was that was causing the problem.
A large shimmering jet black raven. There he was sitting there enjoying the view of himself reflected in the water.
Five times the size of Mr. and Mrs. cardinal sitting on the fence hoping he would leave so they could go for an evening dip.