I have also found that hanging a cluster of cheap feather dusters really helps w/ warmth, it insulates and keeps thier body heat close as they gather under and in it.Your babies need sunshine and fresh air to grow strong. If fully feathered and if the kennel is good at blocking direct wind and weather, they should be fine with a good bedding and a lamp. You want to make sure that the lamp is protected from the elements and has a cover to protect from the birds. If it is too hot in the kennel you will cook them. A 100 watt bulb could be all you need depending on the cubic footage inside the kennel. The will move closer to the light for warmth and away from it if too warm.