Different size chicks in the same brooder?

[Aviphotos]

I have 12 Marans chicks (mix of black, blue and buff black tail) that are about 3 weeks old that have been together in the brooder. Today I picked up 3 Blue Laced Red Wyandotte that are about 3/4 weeks old thinking I could put them all together but the 3 BLRW are quite a bit bigger and more feathered out than the Marans chicks even though they should be about the same age (give or take a week). Will they all be ok in the same brooder together? I'll be separating them when older for keeping the breeding separate but would make life simpler for the moment to have them together, just don't want the smaller Marans getting hurt. Thanks!

 

[azygous]

When the chicks you want to put together are all under four weeks, it's feasible. But there are always temperaments of individuals that can ruin the plan. All you can do is put them together and see what happens, being ready to intervene and go to Plan B. Plan B could be a double brooder with a partition so the two groups can interact but not get physical.

I used to tape two cardboard appliance boxes together and cut a window in the common wall, then glue some window screening over the opening. You will need to provide different intensity heat sources for the two groups since the three-week olds won't need heat during the day while the new chicks will need it around the clock.