Now zoo question but can't seem to find a reliable source. Need to seal concrete bird baths. Losing too much water. Flex seal has been suggested on one site. I want to verify that it is safe. If not what should be used and white or black?

Is this a serious question? Why would you possibly ask this in the question and answer page of the zoo? Are people really this technologically illiterate?

White or clear I'd think. Let it completely dry before use. Doesn't hurt plants when used to line pots... and plants live in it 24x7, doubt it would hurt birds who are in it a few minutes...

White, I should think it's safe as long as they don't pick at it, so if they

Unfortunately I can't help you with that. I have no information.