Cuttlebone, also known as cuttlefish bone, provides natural calcium and minerals for your bird. Birds sharpen and keep their beaks trimmed by using them.
These are recommended for caged birds. It is important to also provide D3 supplementation and proper lighting so your bird can absorb the calcium. Without the required amount of D3(sunshine Vitamin) the bird will not be able to absorb the calcium no matter how much they are given. So with Calcium it is also important to ensure D3 is supplied, which is in most avian vitamins.
Small Cuttlebones are recommended for finches and canaries. You can use larger size but they usually are hard to get into the cuttlebone holder and get soiled before they can be used up.
Keep clean cuttlebone in your birds cage at all times.