Many materials in birdbaths are toxic to birds. I just ordered Burley Simple Elegance, because they use food-grade glazes on their birdbaths. Actually, Simple Elegance is a little smaller than I'd wanted, because robins loved to spread their wings and splash in my old (just broken) birdbath. But this particular birdbath has a locking bowl, which they claim is easy to remove for changing water. The screw-on bowls won't last, if you're changing water as often as you should.
One other thing about bird safety. You MUST change the water at least once a day. In spring, when flocks are migrating, I change the water as much as 4 times a day. This is because birds poop in the water. And you wouldn't drink that water, so you'd better believe it isn't healthy for birds.
If you keep water in the bowl longer than a day, it not only becomes toxic for animals, it breeds mosquitos.
You have to be diligent about this. I use soap and scrub once a week, and am careful to hose all the soapy water out, and down the drain, because birds fly down and drink from the water you leave, and you don't want them drinking soapy water.
I hope this isn't too scary, because birds have so much fun in these baths. It's like their swimming pool. It feels great to give pleasure to these creatures.