You might find it surprising to learn birds use most of their energy just to keep warm. Studies have demonstrated that roughly 90 percent of the energy birds derive from the foods they eat in the wild and at our feeders is used by their bodies to keep warm. This leaves them with precious little energy devoted to reproduction and growth. This is in stark contrast to the green anoles, toads and other reptiles and amphibians living in our backyards. It seems they are able to employ 90 percent of the energy obtained from their diets directly into growth and reproduction.
For this reason, it is always a good idea to offer our bird diners foods containing oils, fruits, and fats. With this in mind, the menu we provide our feathered guests should include such foods as suet, peanuts, and black oil sunflower seeds, as well as dried and fresh fruit.