Locking Punkster and DartMouth in the hutch for a couple of days and nights did the trick. They stopped picking on the others. Trimming off the sharp tips of their beaks might have had something to do with it, also. The method is to wrap the chicken in a towel and clip off the tip, up to but not including the vein. This blunted the sharp ends just enough to lessen any damage they could do. Maybe it took them down a peg but I can’t verify that. When a chicken is debeaked in the bloody and traumatic (to me) conventional way, just about half the upper beak comes off. The chicken can eat but not peck at others.
Now all six are co-existing in the usual way, with only the “get outta my way” or “hey, that bug’s mine” sort of pecking. The little ones still won’t go into the coop at night. Every evening this week I’ve had to pry them off the perch in the hutch and put them in the coop. There’s now a second perch in the coop but it’s not as high as the first due to the slanted top.
Genius inspiration struck today. I took the perch out of the hutch and put in a nest box made from a plastic tub. I cut down part of one side so that the hen could step in and not have to hop to the top rim and then down. I wasn’t quite genius enough, however. I cut the side too low. DartMouth immediately jumped in and proceeded to remodel the place, scratching all the wood chips onto the wire floor of the hutch where most fell through to the ground.
I think I have to do everything about three times to get it close to right.