- At what age can they start going outside for short periods and
As long as I have time to sit and watch them, mine get to be out as young as a couple days. I think it's best to let them get outside and build up immunity to things in the dirt as soon as possible.
- At what age can they move outside full-time?
To stay in the favor of my family (

) my chicks are outside from pretty much as soon as I get them. They're brooded in a large dog crate with a heat lamp till they're large enough to go in the coop and old enough to not need a heat lamp.
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When do you turn the heat lamp off?
Right now in Florida, the heat lamp is completely unnecessary during the day and most nights for my five Silkie chicks (8 weeks old). I've been leaving it off 24/7 recently, because the way I see it, they would more easily die of excess heat than of lack it.