Ninety percent of a bird's diet consists of insects, even those birds that you see at your feeders. In the winter, the insect population (important source of protein) is low and the availability of berries (important source of fat) is limited. In the spring, birds need lots of energy to build nests and families. You can help by making homemade suet, which birds prefer to the bought kind. Lard can be purchased at many local grocery stores - call ahead to make sure that they have it. If you hang the suet near your other feeders, the birds will discover it quickly!