Are Sumatrans good free rangers? i think i have a Sumatran rooster that i hope will look after my flock of a couple RI reds, Barred Rocks, Aracunas and silver wyndots layers. They're a lost bunch and want to  defect to the neighbors flock with out a cock to keep them in line. But are the Sumatrans too wild to let loose?

Sumatras are active foragers.  Like other chickens, they may join a “clique” in another building or in your case, a neighbors flock.  But, I doubt they're any different than other breeds in that regard.