Discourage grackles from congregating by keeping your compost and waste bins covered.
Remove or cover water sources, such as bird baths and dripping hoses.
Replace your current feeder with a caged suet cake model; caged designs can deter large birds, such as grackles.
Pick up a conical baffle at most hardware and home supply stores for under $15. Or you can make your own with aluminum sheeting. Cut a 1 1/2-foot round of aluminum with a pair of tin snips. Slit the aluminum from the edge to the center. Remove a 1- to 2-inch circle from the center of the sheet. Hold the sheet by the edge on either side of the slit and push your hands together to overlap the pieces and form the cone. Apply glue, staples and/or waterproof tape to the union to bond it permanently.
Slide the baffle onto the pole of your bird feeder so that it slopes toward the ground. If you have a hanging feeder, disconnect the feeder, slide the baffle onto the chain then reattach the feeder.