The witches in the tree is a completely different station to the 4 women (1 apart from the group of three).
the witches are to do with the bagpipes, @BobBobBobbing gave the most direct clue:
Witches are part of a clue with the piper underneath. Tbh, unless you know the place you are going to have to look at the wiki page with stations on as it is super obscure. Think about the nationality of the piper, that there's just one of him, his position in comparison to the witches and what they are sitting on