Sleeping with the head tucked into the feathers is probably one of the oldest known avian behaviors. Although it has been recently shown that birds can reduce their metabolic rate by displaying this posture, the energetic benefit of putting the head under the feathers has never been quantified yet. Through the use of infra-red thermographic imaging and a within-individual approach, we compared the heat dissipation of birds sleeping in different postures at a Mediterranean stopover site during spring migration.

If you want to know more about the amount of energy that you can save by tucking your head into your feathers while sleeping, you can access the paper following this link.