I wanted to add a birdbath near the bird feeders so I bought a fairly large (18 inch diameter) plant tray ($20) that has a black glaze on it and set it on a black wrought iron plant stand (also $20). The problem is that the glaze is too slippery for the birds. The birds drink out of it but they won't take a bath, and I watched a poor Chickadee keep slipping into the water when it tried to drink.

I put a flat rock in the water for birds to perch on but they don't really use it. I don't want to use stones on the bottom of the tray because it is already shallow, that doesn't solve the slippery edges, and that makes it difficult to clean. Btw, I have 3 other birdbaths, 2 concrete and one large terra cotta plant tray and they aren't slippery so they happily bath in those.

Does anyone have any suggestions for something that could add some traction to the finish on the birdbath? Here's a photo. Thanks.