Skin and Feathers Deter Ectoparasites

a black and orange bird sits on a tree branch amongst green leaves

Biological Strategy

Black pitohui

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Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.

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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 and skin of black pitohui birds may repel predators and ectoparasites thanks to a steroidal alkaloid chemical obtained in their diet.

“From their diet of berries and insects, they store in their skin and feathers a steroidal alkaloid, homobatrachotoxin (found elsewhere only in poison-dart frogs). Bent Poulson is convinced that the storage of toxins in the skin and feathers is useful for deterring ectoparasites as well as predators. In laboratory tests, lice show far higher mortality on pitohui feathers than on nontoxic feathers; not surprisingly, they avoid feeding or even resting on them.” (Engel 2002:127)

Last Updated August 18, 2016

References

Book

Wild Health: How Animals Keep Themselves Well and What We Can Learn From Them

16/01/2002 | Cindy Engel

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