Fill your feeder with foods that squirrels won’t want: safflower seed (which attracts species such as cardinals, chickadees, and titmice), nyjer thistle (which nourishes goldfinches and others of their kind), or a birdseed mixture that includes a large amount of white proso millet seed (which satisfies the hunger of mourning doves.
Add a tablespoon of cayenne pepper to 10 pounds of birdseed and mixing it well into the seed. I find that the next time they came to the feeder it was probably the smell or the taste of hot pepper…and away they went. After a couple of tries they gave up without eating. It does not hurt the birds evidently the pepper has no effect on birds as they certainly enjoy feeding without interruption. I enjoy your Friendly Bird Tips.”
…from John Mehill