does the scarecrow only last for a few days? then do you have to start again
No, once you have built a Witch Scarecrow it will always work to turn ghostly mice and ducks into zombies. You need a RFH Halloween plant to make them into ghostlies first, though, and you don't have one yet.
how do I get a face for my witch
and Sparkles wrote5 days, 16 hours ago
Leave out bird mix for a crow and when it's spotted it'll carve the face.