motifs. Yes, that's why I mention them.

Actually, 'Rushes a-growing' is at least as common as the ducks and hares, the fish less so.

Child gives all of his sources and dates so it would be a moment's job to check them. You might need to look up the publication dates in Vol 5. I would guess they are older than the English versions.

I agree on 'old tradition'. The theme is also very common in folktales and Child quotes some of these as well.