Walnuts are low in saturated fat and high in polyunsaturated and mono-saturated fat. They are an excellent source of omega-3 and omega-6 fatty acids. They have zero cholesterol and have a good source of fiber and protein. With this being said, birds LOVE walnuts.
Wild birds can be fed walnuts in the shell, on their own, or they can be added to a homemade suet cake after they have been shelled and chopped. Birds that enjoy walnuts include: woodpeckers, sapsuckers, jays, warblers and more.