is this a set of chickens that has been together a long time, and the behavior just started? Or is it a new mix of chickens?
In addition to all the good suggestions above, make sure that they all have their own 'space'. That the ones being picked on can get away, a box, or a pet carrier or some barrier that they can hide in...some place to run to.
Make sure that there is plenty of feed at different feed stations for the chickens, so that the dominant ones don't feel that their territory is invaded by the gold ones. Make sure there is water. So feed and water for the dominant and the less dominant and an extra one so they see that there is abundance for all. ;O)
Think of some things that can relive their boredom. Do they free range, can you throw them a head of lettuce, cooked corn-on-the-cob, perhaps a soccer ball? Seriously, I got a chicken toy that is a ball with holes in it. I filled it with sunflower seeds and the chickens learned that by rolling it they could get sunflower seeds out. I told visitors that my chickens were learning to play soccer. Also think of a forage cake for them-- Resolve is one of the BYC sponsors, and you can get them on line. It contains nutirents and uses their beaks to advantage.
There are also mechanical methods to stop pecking other chickens. One is 'peerless peepers' - It somehow blocks the view line of the chickens from pecking others. There is also something called bumper bits or something that allows the chicken to feed, but not peck others. If I can find links, I will be back to post them.
It's funny how dyslexic I am---it isn't peerless peepers, it's pinless peepers:
http://www.eggcartons.com/Pinless-Peepers/productinfo/PINLESS-P/
And the other device:
http://www.omlet.co.uk/shop/shop.ph...=10750&product_name=Bumpa+Bit+-+25mm+-+Single
Not sure if they are available in the USA.....sometimes the UK is more advanced in chickening than the USA.
BTW Marymary---welcome to the forum!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!