The alpine chough is a species of corvid (name of the crow family) I met high up on the Top of Europe located in the Swiss canton of Valais.
I was there in the coldest month of the year and it was -15°C. But that’s obviously easy for the birds.
Right, most birds are homeothermic, or warm-blooded. They have a metabolism that generates heat as they digest food and exercise.
Almost all birds are covered by two layers of feathers. The inner layer is called down and provides insulation. The outer layer protects the down from wind and rain and provides the flight surfaces.
They also have a layer of fat under the skin that adds additional insulation.
Together with an efficient heart that pumps blood to all parts of the body, a bird is basically a chemical heat source wrapped in a fatty layer of insulation wearing a down jacket.
