Grit is anything that would provide a grinding tool in the gizzard, where the feed is broken down. Tiny pebbles, sand, grit, canary or pigeon grit, etc. are all suitable for adults birds, but only canary grit (or something similar in size) should be used for chicks, when necessary. If your birds are on commercial feed exclusively, then grit is not necessary. If you add grains or seeds, you should provide grit if the birds do not free-range. Under free-range conditions, grit is not necessary, although many feel more comfortable if they provide grit on a free-choice basis. This is especially true if you have a bird that tends to ‘load up’ on grass.