We put out bird food which is a mixture of various seeds including sunflower. Both squirrels and chipmunks prefer sunflower over all the other seeds in the mix. However, they have different approaches to utilization. The squirrels, like the one above, will search through for the sunflower seeds and eat them immediately.
Chipmunks, on the other hand, will stuff their cheek pouches with as many sunflower seeds as possible, then carry them back to their lair. They will make trips back and forth until the seeds are have all been collected. The one pictured below has about all it can hold.