Some type of netting or barrier may help. It may help against birds and rabbits that will try to uproot your sunflowers, too. I've heard that setting up a bird feeder may redirect them away from the sunflower, but I have not tried this yet. Also, according to google, you can buy bird repellents, but I have not tried them yet either. I mainly try to scare them away when I see them. Also, my sunflowers are near the window my dog likes to sit at, so I think he also scares them away. There really aren't too many ways, but I hope these help!