You've probably put out birdseed before. Have you ever tried bird suet?
It's a product you can either buy at the store or mix up yourself at home. For the home version, melt the fat that will harden at room temperature, such as lard. When it has slightly cooled but not enough to harden, you can add various bird goodies. Try seeds, berries, raisins, nuts, oats, or other things they might enjoy.
You can pour it into an old margarine container, stick it in the freezer for a quick set, then pull it back out. It should pop right out. If not, you can cut the margarine container away. You can buy unique holders at the store for suet, or you can hang it in the tree in a bag with holes like oranges come in or even toss on the ground if you have an area where birds frequent. Due to the fat content, though, it may draw dogs if left on the ground to be aware of that.