I am not an expert. Let me be clear. I have heard from the experts, though, and found that there is great value in taking their lessons to heart.
Backyard chickens are awesome. They don’t live forever, though, and for those of us that want productive chickens, you need to keep adding new chickens into the mix to replace those that die or “go to the farm.”
Anyway, I have heard the horror stories from many backyard chicken raisers that have had new chickens killed by the existing flock.
The new chickens that you just got might be sick or carry a disease that could spread to the others. It is very hard to tell that a chicken is sick. A prey species, like chickens, hide their illness and injuries really well, so they are not singled out.
It is best to keep new chickens separate, in a completely different area, until you are sure they are disease free. The time frame may vary, but most people say between a week to a month.
Buy from a reputable raiser, and you should be OK, but better to be safe than sorry.
At Least Two
I have found that you should always add at least two at a time so that the new chicken has at least one friend in the mix. It really helps vs having one chicken singled out by the existing flock.
Keep Separate but in Sight
Provide a space where the current flock can see the new chickens, but not get at them to attack them. I keep my new chickens in a separate coop and run where they can be seen, but not hurt. I even added a net so that I can net off a section of my yard for the new chickens and they can free range near the others without them physically interacting.
The last time, I let them all exist alongside each other for almost a month. By then, they were all comfortable with each other, and my existing flock didn’t endure any stress. Stress will lead to the chickens to stop laying.
By wait, I mean, let the new ones grow until they are similar in size and can defend themselves. Make sure that the new chickens have the ability to get away and hide, if needed, too.
Treats can also be a huge help when it comes to that physical introduction. I spread around some black oil sun flower seeds to they all forage for them and focus on the treats vs each other.
Keep an eye on them when they first start physically interacting in case things go poorly. I haven’t had any issues other than a little pecking order changes when they all fully interact.
What is funny is that the new chickens will, at first, continue to return to their coop at night and the existing flock will return to their coop. That will change, and you may see some visiting between coops overnight. It is like chicken sleepovers.
After a week or so, I will close off the coop for the new chickens and supervise and move some chickens by hand into the existing coop. Every now and then, one of the lead chickens will try to keep the new ones out of the coop by guarding the entrance.
Keep them separated until they are ready to be together.