The first video, called to my attention by reader Michael, describes the adaptive significance of the huddling of emperor penguins (Aptenodytes forsteri), the only penguin that breeds during the Antarctic winter (May-August). Laying eggs at that time, and rearing the chicks, these birds face some of the coldest temperatures on Earth. They deal with the cold, in part, by forming huge and ever-shifting huddles in which the outer penguins move to the warmer inside, and the inside penguins, getting too ho—temperatures can go up to human body temperature 37° C, in the middle—shuffle to the periphery.
This first video gives a nice demonstration of the conservation of warmth through huddling—using coffee cups. The coffee-cup experiment lasts until 1:40, and then it’s onto the penguins. The endless shifting of position is like an avian ballet:
This PBS “Nature” video concentrates solely on the penguin themselves, huddling while they’re holding the chicks on their feet. What wonderful photography! I’d love to see this some day, but few people get to see these birds even in warmer seasons, for they don’t breed in accessible places.