Suet cake

Suet cakes or fat balls are nutritional supplements for wild birds. They commonly consist of sunflower seeds and wheat or oat flakes mixed with suet, pork fat, or coconut oil. Further blends may also contain nuts, fruits, mealworms and other insects.

Next to balls, which are predominantly common in Northern and Central Europe, suet cakes may take various shapes such as rectangles, rings, or wheels. Fat balls are often sold within a fine plastic net allowing their suspension, such as on branches or in bushes, while other forms of suet cakes can be placed within suspendable cages.

Suet cake recipes on the Baltimore Bird Club website

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Wikipedia