I have heard that once chicks have hatched by the hens outside they have to be brought inside and put under a heat lamp because its too cold outside for them. so if that's right then how were chicks raised years ago?
A good mamma will know how to keep her babies warm, even in very cold weather. Some hens aren't as good at this as others and should only raise babies in warm weather or should not be allowed to raise babies. It depends on the risks you're willing to take letting the broody raise her own chicks. So yes, a broody hen most certainly can successfully raise babies outside, but there are also bad chicken mommas who don't do as good of a job.
this is deffidently not true! my broody silkies hatched 8 chicks and not a single one died. trust me just like we have an instinct to not put our babies outside in cold weather they do to and the mama's keep them plenty warm. when i was watching mine if one looked cold she would run over and sit on it to warm it up. ive had a brooder in my house before and it is a pain. you have to clean the box and the birds, feed, and water them everyday. when you have a mama raise them she does everything. all you have to do is feed, water and make sure they are all inside at night
Agree with HeartMoss Farm, that's basically it in a nutshell. It all depends on the quality and reliability of your mother hen. A good mother I'll trust to hatch her babies without help, outside, and free range as soon as she says it's time, even in winter. They're fine. A bad mother can't even do a reliable job in summer.