When a spirit decides to live in your scarecrow, you'll be granted good luck. Crows won't hang out in your farm. Everything you grow will become large and delicious. But not everyone is so lucky that a spirit will decide to live in their scarecrow. So maybe the luck was in you all along!
You want to check the scarecrow to make sure your recent luck is coming from it, so you kick it. "F*** (ふく) you!" it yells. Oh yeah, there's a spirit in there.