I use Sunflower Hearts to keep the mess down that the birds make. The bigest feeders I have are the Goldfinches but they leave what appears to be a clear type skin that has come from the Sunflower Hearts. Does this happen to all Sunflower Hearts or should this have been removed with the outer shell? It makes a lot of mess and it is quite obvious that the birds are not able to digest this skin.
Paul
Paul