i suspect the adults will be feeding chicks and they are getting the food wet due to the dry weather. when you disturb them they drop the food and fly off. if you do cover the bird bath they will go else where. why not cover the fountain too just for a couple of weeks. the crows are clever birds and will soon look else where.

You might want to try an owl decoy. Most birds are terrified of owls. The crows will move on to 'greener pastures' hopefully before they discover the decoy isn't real. Some sport solar powered life-like movement. They are still being used today for bell towers and balconies. .

Yes I guess I’ll have to bite the bullet and cover them.one of my pleasures these days are watching the birds enjoying the bath but if it means the crows going somewhere else then it will be worth it.They stand on the edge and pull off the bits they want then leave what they don’t i the water.the number of times I have to wash it out! Well I suppose it’s taking up a good bit of the day just now.

An owl decoy wont work sadly, crows will attack owls to move it on. The Council put owl decoys up in one of the local market towns and kept finding them on the ground. It was the rooks but they are in the same family as crows.

It doesn't make any difference to your problem, which sounds horrible, but there is an old country saying:

"A crow in a crowd is a rook and a rook on its own is a crow!"

I don't know how true it is but maybe it's a good rule of thumb.

I'm having trouble with magpies here, gleefully raiding the songbirds' nests. It's distressing, but at least they are not doing their butchery in my birdbath. It must be really horrid to deal with. I hope you can solve the problem.