hi i have been putting newborn chicks straight from under the hen in with chicks that were born on the 16th of march... everyone gets along fine.... look at pics in New brooder pics of mine and you can see it will be alright....
I have had this happen so many times! Here's what I have done and never had anything bad happen. I have been able to stick my day old chicks in with previous chicks who are up to two weeks old. I usually hang out with them for the first hour in introducing them to the old gang. I have a little water container that I dip the day old chicks beak into and the older chicks will drink from as well--they're teaching him how to drink. I keep an old wash cloth in the middle, under the lamp for the chicks to snuggle up on...this also gives them a place to nest down while the other older chicks run around them--they don't seem affected by it at all. The older chicks know this is the designated resting place, so they only come there to nap or snuggle with the other chicks. However, with the water, for the first 24 hours the new chick is in the box, I remove it from the box if I am not there. Reason being, day old chicks are pretty wobbly--they tip backwards and sometimes end up on their backs and have a little trouble getting themselves up--for safety reasons I remove the water while I'm not there, so there's no chance of a baby falling backwards into the bowl and drowning while trying to get back up. I check on them every 2-3 hours and give them their water bowl back while I'm in the room. The older chicks do fine with this--they take a few drinks and are fine for a couple hours without. When introducing a new chick, I encourage the older chicks to eat--the new chicks see them eating and mimick what they see--so they start trying out eating. After 24 hours, I place the water back into the box and all is well--they all do fine together and have established a bond(young and old). I just went and checked on them this morning and my two babies that hatched 2 days ago are snuggled up nice and warm with my one week and 2 week old chicks. By the way, I have chicks that are about three weeks now--I have moved them to a seperate box, just next to the other box--with all the same amenities(water, chick feed, etc) minus the brooder lamp. I just keep a small heater that comes on automatically(little box heater at walmart for about $20) and keeps the room nice and warm...they were switched over about a week ago and are doing completely fine. I've never lost a chick to this and have done this MANY times!
Good luck and let me know if you have any more questions!
Hey Jonathon, just adding my two cents as I went through this 2 weeks ago.
I had some three week old chicks and brought home some 2-3 day old chicks. I put them all together and the 3 week old ones (especially the top male) started pecking the little ones on the heads and chasing them into the corner (away from water, food, and the heat lamp).
I am sure it depends on your birds and perhaps the breeds. For me, I wasn't taking in chances. I got another heat lamp, food trough, and water container for the little guys. I then divided the two areas of the brooder with a large (high) piece of cardboard. Since these chickens will eventually have to interact, I cut a small hole in the cardboard big enough for the new chicks to go into the "Big Chicks" area, but NOT big enough for the older chicks to go into their side.
It has been about two weeks now and everyone is getting along great. The little chicks still hang out on their side when they sleep, but go back an forth all day long. Just remember to keep adjusting the size of the cut out as the chicks grow.
I have done the same thing and currently have banty's and game chicks from 3 days to 2 weeks in same brooder all snuggled up and quite happy. The older one's teach the newer ones how to eat and scratch and dust bathe.
Banty's will go under broody hen with other chicks tonite and more game chicks will be added today to existing crew. It's a continual thing with staggered hatches. Let me add, you do need to watch them - there will be the occasional aggressive chick and you will have to separate them.