temporary housing suggestions

[meadow house]

Looking for some good (cheap, free) ideas. I have a very secure predor proof run. I have 3 very feathered out 7 week old chicks that have been outside for a week now. We are getting lows in the upper 30's at night, and I have been moving them into the coop under the top of a wire guinnea pig cage for the night time (so the big girls leave 'em alone), and then outside in a speperated by wire part of the run for the daytime. Any ideas for a temporary shelter that would keep them warm enough so I could quit haing to move them every am/pm? I cut a big hole in a cardboard box and put shavings in but they huddle together on top of the box and don't go in...maybe the box is too small?

 

[Animallover606]

well what what if you put a heat lamp over them in a dog crate