Suet
Made from rendered beef fat often mixed with nuts or other bird-attractive ingredients, suet can help attract a wide variety of birds. Like peanuts, suet is a low-mess food which appeals to insect-eating or omnivorous birds like woodpeckers, jays, bushtits, chickadees, and nuthatches more than the mostly vegetarian house finches and goldfinches.
Suet is sometimes thought of as a winter-specialty food, but it can be offered successfully all year round. It is true that in winter suet becomes even more attractive to birds needing to replenish calories lost just keeping warm during cold temperatures.