Keeping Birds From Putting Food Into Bird Bath?

Debra, you seem to be a nice caring person with having a birdbath for feathered friends, unfortunately that's what some birds DO, soak their meals in water. Not sure what gross body parts? Severed parts of other birds? Worms and grubs?
Unless you can find a way of keeping the big black birds out of your garden altogether... or lateral think.. a big old dish of water somewhere where the birds can go instead, and they may leave the bird bath alone.