Our yard in fenced in and for the most part our chickens stay in the fence. Lately some of the bantams have been going through the fence to get to the park beside our house. They wander around the front yard before coming back into the yard.
Bantams are rarely known for eating plants. They are mainly interested in bugs. I am not too worried about them going out past the fence. Of course the girls have a rooster or two nearby to keep them safe.