Feathers Protect From Water

Biological Strategy

Penguins

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Protect From Excess Liquids

While water is essential to life, too much water or other liquids can overwhelm living systems. Excess liquids can, for example, decrease a living system’s access to oxygen, promote excessive bacterial or fungal growth, or strip away soil and nutrients. To prevent the accumulation of excess liquids, living systems must control the movement of liquids across their boundaries or surfaces. They do so using waterproofing materials or structures, slowing flow, and/or facilitating flow to move the liquid away. Plant leaves, for example, commonly have waxy surfaces comprised of water-repelling chemicals to keep water from engorging the leaves or facilitating bacterial and fungal growth.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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The feathers of penguins prevent water from penetrating to the skin due to their stiff, tightly packed structure.

Image: Featherfolio / Wikimedia commons /

Rock Hopper Penguin Feather. Large shaft and lots of down keep the penguin warm

Image: Matt Browne /

“The penguins (below) lost the power of flight some 100 million years ago, and have no flight feathers on their wings. Their stiff close-packed feathers form a thick insulating mat that is impervious to water and provides a good streamlined surface for swimming.” (Foy and Oxford Scientific Films 1982:111)

“Several studies have investigated the thermal resistance of penguin ‘coats’ (feather and skin assembly) and found it to be surprisingly low—an average of 0.74 m²KW^-1 or 7.4 Tog. Penguin feathers are heavily modified, being short (30-40 mm), stiff and lance shaped. Insulation is provided by a long (20-30 mm) afterfeather. Penguins are unique in that the feathers are evenly packed over the surface of the body (30-40 per cm²) rather than arranged in tracts. For insulation the penguin requires a thick, air-filled, windproof coat (similar to an open-cell foam covered with a windproof layer) that eliminates convection and reduces radiative and convective heat losses to a minimum. However, when diving, the penguin requires a thin, smooth and waterproof coat with no trapped air (positive buoyancy would be a big disadvantage to an active swimming hunter). It achieves this by using muscles attached to the shaft of the feather to ‘lock down’ the feathers to create a water-tight barrier. In addition, the feather rachis is flattened dorso-ventrally allowing it to bend and conform to the body shape readily with increasing water pressure.” (Dawson et al. 1999:199)

Last Updated October 24, 2016

References

Book

The grand design: Form and colour in animals

26/02/1983 | Sally Foy

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Reference

Journal article

Heat Transfer through Penguin Feathers

Journal of Theoretical Biology | 07/10/2002 | Colin Dawson, Julian F.V Vincent, George Jeronimidis, Graham Rice, Paula Forshaw

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