Feathers of penguins trap air to retain warmth by being filamentous and forming a continuous layer around the body.
"As insulators, feathers are even more efficient than fur. Only a bird--the penguin--can survive on the Antarctic ice-cap in winter, the coldest place on earth. The penguin's feathers are devoted entirely to this task. They are filamentous and trap the air in a continuous layer all round the body. This, reinforced by a thick coat of fat just beneath the skin, enables the hot-blooded penguins to stand about in a blizzard in temperatures of forty degrees below freezing and remain there for weeks on end, even without stoking their internal warmth with a meal." (Attenborough 1979:178-179)
Learn more about this functional adaptation.
- Attenborough, David. 1979. Life on Earth. Boston, MA: Little, Brown and Company. 319 p.
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