I didn't know that about weedkiller.

I do know that Slug Pellets (Snail Killer?) kill both Song Thrushes and Hedgehogs, and probably anything else that snatches up the dying snails. In the case of Hedgehogs, it kills them very slowly, and I have to finish them off as a mercy killing.
I wish my gardener neighbours wouldn't use it.

Frogs did breed in my pond one year. The tadpoles lasted until the goldfish realised they were edible.