I've had chicks since April 12th. They didn't have wing feathers until a few days after we brought them home. Their brooder is a 4x2x2' galvanized tub and we have 5 novogens. They are super attached to us and come close when called. They let us pick them up and are pretty friendly and mellow. Anyways...., Once they got a good amount of feathers, and it was warm enough outside (60's+) they've been spending their days in the chicken tractor (big enough for 10-12 birds) outside. At night, we tuck them into bed...I mean brooder and turn on heat lamp because it's been in 40's at night. Well they've been trying to jump out of the brooder and excited to get outside that I figured I would try to let them sleep in the tractor (has a coop area and nesting box). When the sun was soon to set, I set the heat lamp up in the coop area, ran an extension cord to the tractor, filled their feed and after they all had their fill, they'd start crying peep, peep, peep at the door. After a few minutes of them huddling at the door and crying so loud we could hear them indoors, I went out and brought them into the brooder. This has happened 3 nights in a row... Are they just too young to be outside at night? Am I doing something wrong? They'll follow me to the garage and right up to the brooder so I can put them in. If I don't put the top on, they'll try to fly out...but don't go far. I don't know what to do. Any advice would be helpful. Thank you in advance.