Thanks for the replies.
Are they though (at a disadvantage)? Even one "against" two, the little ones are still frightened of everyone and the "big girls" scare them (even if they aren't doing anything "mean"). I originally thought I'd put one big girl in with the new girls, but the big girl was so distressed at being separated from her "pack" that I just had to let her out. If they are stressed by having their whole life disordered, might that not cause them to fight, rather than just go "oh well, things are different now, better chill". I'd thought that food might get them all forgetting to chase, or run away, I put a box of veges in the run, but the new girls wouldn't go near the big girls. I'm not sure that they've got anything to be scared about, whether the big girls are really giving them stick or whether it is just them displaying their natural "prey-animal" bird behaviour. I think the big girls would have been more focussed on seeing what was there to fling about, rather than chasing people.....
It's fascinating, really, watching the interactions and behaviours. When you are (relatively) unfamiliar with them, you think chickens just wander about, pecking the ground, but there's a lot more going on there than one imagines.
The new girls moved in on 11 January. My backyard is big. Unless they are put together, they just don't seem to notice anybody else. There's been no "looking at each other through the fence" or anything, they've just ignored each other.
Edited by potato chip - 2/17/16 at 3:58pm