Cuttlebones are traditionally used by jewelers and silversmiths as molds for casting small objects . They are probably better known today as the tough material given to parakeets and other pet birds as a source of calcium for their diets . Jewelers and silversmiths traditionally use cuttlebones as moulds for casting small objects but they are probably better known as the tough material given to parakeets and other caged birds as a source of dietary calcium .