They don't have ways to break food down, so they eat rocks to help digest the food.
Discussion
Wow. I did not know that. Very interesting. Thank you.
Common in most fowl actually, especially those with a gizzard. Although most fowl need pebbles much smaller than this.
Kinda like tumbling spent cartridges to clean brass before reloading. The tumbler being the gizzard that needs the aggregate and the reloading being the "true" stomach that requires microbes.
Love the reloading metaphor. 👌 thanks for the info!