Hi, We have fostered many day old chicks onto our broodies. It works really well, and allows you to expand the gene pool if you get the eggs from unrelated families. My experience is that you need to get the chicks really new, preferably day old, when they will accept their new 'Mum'. All broodies will accept a chick of this age, as long as they have sitting long enough to believe that it is their own. this means that she needs to have been sitting for 3 weeks. You don't necessarily have to remove the old eggs. She will sit tight on the chicks for two days and then, if the other eggs haven't hatched, she will abandon them as infertile. Tuck the chicks under her, the cheeping will immediately alert her to the fact that there is a live chick there, and she will nestle over them. Stick around. If she abandons any of the chicks she will push them away from her. I have never found this with day-old fostered chicks, but I have found it with eggs that have hatched many days apart, where the Mum has decided that she has already had her brood. Chicks more than 3 days old may not accept their new 'Mum'. I have had a broody fly out of my arms and straight across the room to where the chicks were and then nestle them under her. She didn't hatch them, but they were babies and she wanted them. I had a chick hatch from the egg in my hand last Monday, and then presented it to the Mum and she instantly took it over. Don't worry, the instinct is very strong. Hope this helps.
