merging old and new flocks

[honeyk]

I have 15 older hens in the main part of our chicken house. I have 35 11 week old chicks in a pen next to the main chicken enclosure.
The main enclosure also has a chicken door out to a very large area protected by electric netting. The younger birds no longer want to be confined in the pen. When would it be safe to merge the two flocks?

 

[Pumpkinpup]

I would not do it until the chicks are mostly mature. As long as they are making "Baby" sounds, the adults will be very agressive toward them.