Can I combine?

Yes. There shouldn't be any problem if they're only a week apart in age.

 

I did the same thing. I wanted a certain breed and only one lousy egg actually hatched from the 13 eggs I bought from Ebay, so I bought day olds a week after the others had hatched. I had also hatched 5 of my E Eggers. So I now have 21 week old chicks, and 6 two week old chicks in the same brooder. At first I put up a little divider so the day olds wouldn't get abused by the bigger chicks, but I took that down after 3 days. Even though the older chicks are just a week older they looked like huge prehistoric giant birds next to the little ones. But they seem to get along just fine. It was actually really fun and interesting watching the younger chicks stand up for themselves when some of the older ones tried to peck them. Some of those tiny chicks simply were not having any of that! Just make sure you have plenty of feeders because the older ones will try to push the younger ones away from the food.

 

I was worried for a minute about the same thing. I was waiting for our TSC to get in the chicks that I wanted and ended up falling in love with the australorps and had to get some. It was almost a week later that they got in the comets and the tetra tints . I figured I would put them together and if that didnt work I planned to make another brooder. The older chicks pecked at the younger ones alittle but I was really suprised at how well those little guys stood up for themselves !!

Chrissy