Sunflower seeds, both in and out of their shells, deserve one of the top spots for bird seed to feed garden birds. Many species are attracted to eating sunflower seeds making them a very versatile bird seed. Leaving out sunflower seeds will attract species such as nuthatches, cardinals and grosbeaks. Sunflower seed hearts are also a good choice if you're looking for a no mess bird seed. Sunflower seeds are suitable for use in most garden bird seed feeders.