My friend has just got some chicks. They seem happy and shes just started to put them outside in the coop to sleep. They don't want to sleep in the nesting boxes. They sleep in the metal tray under the perches (I think that's what she told me. She's really worried they're cold. They seem to be snuggled up together and don't look very warm. Is there anything she can do to train them to sleep in the nice warm nesting boxes. Thanks.