I can only tell you about the 3 times i introduced new members to the coop/run over the past 4 weeks...my coop is big enough to hold about 50-60 to sleep...my run is 25x 75 feet...i was just as worried as i know you are...the first batch now 4 months old no worries they were first.. (10) chicks...the second batch a week later...had not been kept with the first different breed 9 of those and 4 wellsummer about the same age...i took all 13 in run and let them out and stayed in there for about an hr just watching...everything went fine...next morning the 2nd batch was outside foraging...1st batch came out and straight to me...3rd batch the next week smaller only 6 i did the same thing ...all was fine except for 1 large hen/chick grabbing 1 of the smaller new chicks and pecking it...i was right there and gave her a nice tap on her head ...scolding her...anyway i think that if they have enough room and there are multi spots with food and water around your run...its gonna be ok....but supervise...its been a week and all of mine are doing great...everyone knows there place...all forage eat...chase bugs...happy chickens....good luck...oh i also gave them all scratch in run at the same time all over the run (when i added new chickens)...like chicken candy to them...
