We hit a warm streak last weekend, so I made the executive decision that it was time to set up the chicks' sun porch. It's extremely ghetto, but--as it's also extremely temporary--I've found it's a good way to let the chicks have outside time even when I can't supervise them. Here's what I do.
Once the chicks are starting to feather up, I move them from our little rubbermaid-tote-brooder to a dog x-pen, with cardboard around the sides to keep out drafts. Then--a week or two after that, or when the weather is warm enough--I wrap a long piece of chicken wire around the poles of the awning on the front of our shed to form an enclosed, outdoor space. Then, after making sure the path between the x-pen and the front door of our shed is a pretty straight shot, I open the doors.
It usually takes the chicks about 5 minutes to get it, but when they finally do, it's very exciting. They can go in and out, completely on their own. They can take dust baths and fly at each other outside, but still run back in and warm up under the heat lamp if they get too chilly.
It's not 100% predator proof, but it's not bad. While a neighborhood cat could still pick a chick off--a problem we haven't had yet, knock on wood--the awning above provides protection from overhead predators. And the chicken wire keeps out the bigger ladies, too. (They won't be introduced until much later this summer.)
On colder days--and at night, of course--we still have to lock them up more securely. But I do feel better leaving for work on these nice, Spring mornings knowing that my little chooks aren't going to be cooped up inside all day.