We touch keratin every day of our lives. It makes up our hair, nails, and some clothing. The keratin present is mammals is called α-helix keratin, which you can think of protein folded in a helix. The same protein that makes up these materials is what the feathers of a bird, but it is folded differently. Imagine a helix stretched out and then made into sheets, we will call this β-sheet keratin.
Research has been done to determine if feather stiffness varies among bird species. Surprisingly, it has been found to not. This leads us to the conclusion that feather strength is fairly uniform among birds of different sizes, and that a feather’s mechanical performance depends more on the shape of it.
Micro hardness tests have been preformed on feathers containing melanin, and some feathers not. Melanin is a pigment that causes black and brown pigmentation. The tests preformed on these feathers have concluded that darker wings, ones with the pigment melanin, are significantly harder than wings without melanin.
The archaeopteryx, a commonly researched prehistoric bird, has been determined to have black wings. The black color of these wings is most likely due to a large presence of melanin, which would make the wings significantly stronger because of more durable feathers. This makes sense because the feathers probably had to endure the harsh late Jurassic conditions.
Feather strength has been found to vary in migratory birds and sedentary birds. The variation has been found not in the strength of the material, but composition of the components of the feather. In a study of migratory and sedentary blackcaps, it was found that both variations have the same feather mass and rachis (the “shaft”) width, but different bending strength. This led to the conclusion that the migratory birds allocate the resources they have to construct their wings differently than sedentary ones. Some possible explanations of this are that migratory birds have weaker barbs, which would make the feathers light, stiffer and weaker. This would also explain the more frequent molting of migratory birds.
In conclusion, the feather materiel in birds does not vary significantly between different species, but bird size and frequency of activity does influence the size of individual feather components.
- De La Hera, I., Hedenström, A., Pérez-Tris, J. and Tellería, J. L. (2010), Variation in the mechanical properties of flight feathers of the blackcap Sylvia atricapilla in relation to migration. Journal of Avian Biology, 41: 342–347. doi: 10.1111/j.1600-048X.2009.04835.x