Suet Blocks are strong in high-energy fats, which are essential for wild birds throughout the winter months. Other components such as mealworms, fruit, and insects can be used. Lard/suet, nuts, grains, and sunflower seeds are used to make this dish. As a result, they are tightly packed with the energy and lipids that birds require. Other tits, sparrows, starlings, blackbirds, and black caps also enjoy fat balls.