If you are trying to save the seeds to your sunflowers then you need to put some sort of bag over them once the seeds start developing. I have large burlap bags that I just throw over top of the heads. I've also used old pairs of boxers, which usually give visitors a good laugh. You want to make sure that the heads can breathe or they will mildew. If there is a heavy rain, then you want to change the wet bags with dry ones. Sometimes the squirrels will try to chew their way through the bags. They will also chew their way through the stem to get the head on the ground. There isn't much you can do to stop that. Another thing to distract the squirrels is put large amounts of sunflower seeds somewhere else in the yard, away from your crop. I usually fill the bird feeder with seed, and then throw seed on the ground around the bird feeder every day. The squirrels spend most of the day rooting around in the grass for seeds, and ignore my sunflowers growing in the garden.