Adding baby chicks to your flock is an exciting time for you, but it may not be such an exciting time for your chickens. Chickens are very sensitive to changes in their routine, and that can cause stress in the flock. Mature chickens can become bullies of smaller chicks, keeping them away from food and water, attacking them, and just being plain ol’ mean.
Your flock will be most accepting of chickens that are similar in size, and most chicks are considered fully grown at about 16 weeks (although hens may not begin laying until 6 months). You can keep your chicks separate from the flock for 4 months and integrate them then, or you may consider slowly introducing the smaller birds to the larger ones to ease the transition and make the addition sooner.
At around 8 weeks, you can suggest the idea of new chicks to your existing flock by placing the chicks in a cage, or by separating your chicken run or yard to separate the two groups. Just being in the same area as the chicks allows the chickens to study them without being aggressive. Be sure to set up a separate area for the chicks in the coop, as well, that will include their own feeder and waterer for nighttime.
After a couple of weeks of the chicks and chickens living separately but together, the chicks mingle with the full-grown flock. Take down the separation during the day, allowing the chickens to forage together. You will also need to make sure that chicks don’t have access to the flock’s layer feed. Owners will often switch the entire flock over to chick starter during this transition period; just be sure to provide supplemental calcium to your laying girls. Continue to keep the mature birds and chicks separate at night.
After one or two weeks of this, it should be safe to let the chicks join the flock without restrictions. You’ll need to stay vigilant the first few nights to quell any unrest, but your chickens should be used to each other by this point. If any chickens are found injured or bleeding, isolate them until they are healed.
Co-mingling your new chicks with the existing flock can cause some anxiety, but with patience and time, the chickens should come together seamlessly, boosting your flock’s numbers and spirits.