If you didn't hatch the chick yourself you should quarantine it. Store bought or hatchery bought chicks can carry illnesses that can harm your flock. I've heard of entire flocks dying from not quarantining foreign chicks/chickens.
The method I use for my chicks is a keeping them in the brooder (in my garage, far away from the flock) until about 6 weeks old, I usually get two chicks at a time so they have a buddy with them when they are put into the flock. At 6 weeks they are usually big enough to defend themselves or get away from the older chickens. When putting them into the flock I put them in a large dog cage, or wire a section off of the coop where the new chickens and old chickens can watch the pecking order without being able to fight or touch each other. After four days I allow them to walk in and out of their area freely letting everyone free range. They get picked on but usually allowing them to free range distracts everyone so their isn't too much damage done to the newbies.
If these are hens, I'd quarantine them for two weeks minimum, then use the same method of separate but visible to each other.
I've been very careful with introducing new flock members, with this method not once have I had any blood. I must add, my chickens have always been introduced in pairs so that one chicken isn't taking all the damage.
I hope this helps you!
Crysta
