Editing Gizzard (section)

===Gizzard stones===
Some animals that lack teeth will swallow stones or grit to aid in fragmenting hard foods. All birds have gizzards, but not all will swallow stones or grit. Those that do employ the following method of chewing:

{{quote|A bird swallows small bits of gravel that act as 'teeth' in the gizzard, breaking down hard food such as seeds and thus helping digestion.{{sfn|Solomon|Berg|Martin|2002|p={{pn|date=January 2025}}}}}}

These stones are called ''gizzard stones'' or ''[[gastrolith]]s'' and usually become round and smooth from the polishing action in the animal's stomach. When too smooth to do their required work, they may be excreted or regurgitated.