Back yard grass follow up

I finally got grass to grow in my back yard.  And now the chickens are already starting to tear it up.

I have an entire back yard for them to wander around and they have to go for the area that hasn't had grass since I moved in (until just recently anyway).  There is a lot of clover in that area.  I'm guessing that's what they are after.  I'd prefer that they just eat the tops, and not scratch it up.  Oh well, I eat their eggs so I guess they figure that they can eat my yard.