Jason E. Andersen

Bonus fun fact: Have you ever wondered how birds can stand in freezing cold water without getting frostbite? Birds (and also some fish, marine mammals, and humans to a lesser extent) have what is essentially heat exchangers in their extremities. The blood vessels responsible for transporting blood to and from the extremity are very close together, touching in fact, so heat can be passed from one vessel to the other. As warm blood flows towards the feet, the heat energy is transferred to the cold blood in the other vessel, which has already passed through the extremity. Effectively, the heat takes a shortcut while the blood has to flow all the way around. In this way, the blood in the feet is always cold, keeping precious body heat close to the bird’s body. It’s quite efficient, just ask any bird!