Really need pictures of your set up. You have to determine your risk level. I have often got birds from somewhere else, but I know what I am risking.
You are risking a high number of birds. If I have the count right, you currently have 30 birds, + a small garden flock? Is there a rooster in those groups? You will add another 15 head, bringing up the total to 45 head +/-. If I understand correctly you are trying to bring 4 different groups together - 2 you currently have, and 2 separate groups making 15 birds.
45 x $20 = $900 flock that you are risking.
When one adds new birds, these things can happen:
- everyone stays healthy, and eventually become one flock
- Adding birds is stressful, and can bring on latent diseases
- original birds get sick from new birds
- new birds get sick from old birds
- everyone gets sick as you are combining 4 separate groups.
A lot depends on where you are getting the birds from. Is it a person that like you, have chosen to raise up some birds. Those birds have never been exposed to other birds, or other birds' diseases. These birds are healthy, with good feathers, bright eyes and active. In away, these birds are in quarantine from your flock in their current home.
Or is it a person that attends auctions, or shows, where birds are exposed to a lot of different birds, and could bring home a disease. Personally, I would not add auction birds, the Lord alone knows what they are exposed to.
Or is it a group of birds you feel sorry for in their current set up. Don't ever buy birds you feel sorry for. That is a good deed that is often punished.
Can you cull birds or immediately separate them out a LONG ways away if they start to sneeze or cough or show other signs of illness to prevent it spreading? If this happens, immediately remove the sick birds, throw out all the food exposed, clean feed bowls and water bowls with a chlorox bleach solution, rinse well, rinse again. I would also change out the bedding in the coop, nests, and anywhere else you have bedding.
A lot of diseases are air bourn, so one needs a great deal of distance between them. Integrating birds - getting them used to other strange birds by separating them but within sight is NOT quarantine.
As stated above - a lot of people cannot separate birds by 300 feet, change their clothes and shoes before taking care of the other birds. And if you don't do it correctly - well you really can't cheat at quarantine, and you may as well not do it at all.
If you go into an emotional decline if you loose one or several, don't get them, the risk is real.
Mrs K