Black Oil Sunflower seeds 40 lb is by far the favorite seed of most all backyard wild birds. Sunflower seeds will keep the birds coming back to your backyard for more. If you have only one seed, this is a excellent one to keep a good supply of. There should be a least one dedicated feeder that offers black oil sunflower seeds. Make sure your feeders are protected though, as other uninvited guests like it as well!