Fine Sunflower Hearts Wildbird Food Can Be Served In A Thistle Feeder Or Added To Other Seeds In A Mix. Because the shell is gone you will have less mess at the feeders. Because the shell is gone you will need to be extra careful to keep it dry, clean and not offer more than a couple of days supply at a time. These small chips mix well with Thistle. Fine Sunflower Hearts Wildbird Food is sold by the pound.