The Pine Tree Farms Black Oil Sunflower Seed Bell provides a great source of high energy to your backyard birds, which have a very high metabolism. Seed bells are a great alternative to loose seed feeding. 11 oz. Pine tree farm s seed bells are a great way to attract birds into your yard. Seed bells are packaged with colorful net that is ready to hang on trees and shrubs. Black Sunflower Seed.: Size: 11 oz.