A lot of birds like safflower, especially Northern Cardinals. Squirrels aren’t crazy about it. That’s because safflower is bitter tasting. (Birds don’t have a sense of taste like mammals do. More on that later.) So, try removing all of the other seed from your feeders (except your finch feeders) and replacing it with safflower. Chances are it will drive the squirrels to a new food source. But keep in mind, they will probably come back eventually when you start stocking black oil sunflower again.