I was able to do it not once but twice.. About a 2 or 3 week difference in all my spring chicks, Although I didn't add one or two. When I added chicks it was ten or more... I would use your own judgment, it may not work and you should be ready to separate or remove them.I have 20 chicks in my giant brooder that hatched on Monday. The next batch is set to hatch Wednesday. So here's the question...can I put the new babies in with what will be 1 1/2 week old chicks? My brooder is 4'x7' so space isn't really an issue. Do I need to add a divider?