I myself leave my chicks out from time I get them at a day old no more than a week old... I have heat lamp outside a brooder tilted to heat the inside, inside the coop that is surrounded by netting filled with much older birds. This is during the slightly cold to warmer months (temps 50-70+) the brooder seems to keep pretty warm even when temps outside are pretty cold and the chicks show no sign of being cold (huddle together) they just carry on a normal chick life inside a brooder... Does anyone else do this? I always read things bout chicks need to be at least 2 months old or around there before they are put outside... why? My birds are well grown now and free range all day then go back to coop at dusk when dusk to dawn light comes on, I see NO negative affects of the way I raised my birds they are happy, friendly, and very healthy.