andisgarden, most of the above is true. I have to throw in my 2 cents. I breed gamefowl and if any youngsters are gonna start trouble, gamefowl will.
To begin with. Most mature cocks will not harm chicks. Hens are the ones that give chicks a hard time. I usually pen all my chicks after they are weened, with a mature cock. At about 5 months of age, I take out all the pullets and leave the boys to be policed by the cock. The idea is, if anyone is gonna whip butt, it`s gonna be the cock. At about 8-10 months, the boys "turn on" and I start moving the trouble makers to solitary confinement. Your barnyard types will seldom need this radical confinement. So this is just a little trivia for you to ponder.
I also breed Asils. They are extremely hard to raise as they often engage in mortal combat before they are fully feathered. They break wings, legs, and even necks resulting in death and seem to know when you aren`t home to start these battles. The girls fight as bad as the boys.
Again, barnyard types seldom have more than we call "chick fights" which are mostly play. The only reason I`m telling you all this is so you see how minimum the "fights" are in your yard. At 2 1/2 weeks your girls are as rough as the boys. Have fun with them and don`t take them to seriously unless things get really rough.