Carobean here, with an update on our resolution of the 6-hour car trip (originally posted almost 3 years ago now!): Although I liked the handwarmer idea, I wasn't sure they'd keep the box warm enough (I guess it probably would've, judging from the many posts about this method...), and didn't want to have to keep changing them out. My husband ended up wiring a small lightbulb that I could plug into my cigarette lighter-power-outlet thing in my car. I made a hole in a small cardboard box (half-shoebox size), and made a guard for the bulb so the chicks couldn't burn themselves on it. I practiced driving around with the box plugged in, with a thermometer, and found that the bulb heated the box up nicely, warmer than other methods we'd tried. Every half-hour or so the girls would start hollering, and I quickly learned that meant they were hungry (I didn't leave food in the box, but probably should've), so I'd pull over and give them some crumbles. This was a good bonding experience, and they quickly learned that I was the Source of All Food and Water, and I quickly learned that they eat a lot! The five of us arrived safe and happy after a 6-hour drive.