I have a small brood (4) of coturnix that is 4 days old and want to know if I can add several (probably 6) coturnix that are hatching today to that brood once they are a week old. Thoughts? Anyone have success doing this?
Yes, they'll be fine. Last time I hatched I didn't think our birds were overly fertile (being older birds) so kept adding eggs for a week after I started. The different ages were fine with each other. Just keep an eye on the younger ones - some need more encouragement to eat and drink and wait for you to help them rather than copying their brothers and sisters.
You might want to put them together when the new ones are 3-4 days old instead of a week. The younger they are, the better they integrate with new birds. The older birds are only four days older, so it shouldn't be a problem.
I have done this successfully many times with chickens and quail. They're not old enough yet at that age to care much about who's with them - bullying starts later. Good luck with your chicks!