Grit meant for chickens contains ONLY crushed gravel--mostly granite. Parakeet grit almost always contain calcium and other minerals meant for caged birds. Baby chickens can be killed by too much calcium intake. You don't even give laying hens food with extra calcium until they actually start to lay eggs. Since chick grit is readily available wherever you buy chicken feed, why not buy what is actually meant for them? Parakeets don't even need grit--they are usually given grit to get the extra calcium and minerals into the bird.