Feathers — Part 1

by Mike Stiles

I recently was introduced to the book "A Guide to North American Bird Feathers" by Scott and McFarland. Much of the information in this article is from that book, and I can heartily recommend it.

The insects, several groups of reptiles, a squid, two groups of frogs, three groups of fishes, and seven groups of mammals have taken flight — albeit some are just gliders. But it's the birds that have evolved the wonderful adaptation of feathers that have allowed them to rule the skies. Two hundred million years after birds first appeared in the Jurassic period, the number of bird species inhabiting the earth sits around 9,600 species.

In a German limestone quarry in 1860, workers unearthed the first known feather fossil that was well over 100 million years old. The next year, a nearly complete feathered fossil skeleton was found and named Archaeopteryx or "ancient wing." Recent finds include non-avian dinosaurs that also had feathers, suggesting that feathers came long before the origin of flight. Even more advanced fossils have been found in China, Spain, Argentina, and Australia.

The feather, made of keratin, the same material that comprises hair, nails, horns, and hooves helps hummingbirds to hover and fly backwards and falcons to fly over 200 miles per hour, allows incredible feats of migration, provides insulation, and waterproofing, and coloration that provides camouflage and ultraviolet protection. The insulation quality of feathers is unsurpassed, as I can attest to in my down sleeping bag.

The feather is comprised of the quill, the bare part of the shaft below the vanes (the actual feathery part), and the rachis, the portion of the shaft where the vanes are attached. The feather vane, or web, is made of interconnecting barbs. Each barb is covered along its length in barbules, and each barbule is covered by barbicels that interlock with each other upon contact.

This three way connectivity gives the feather great strength while allowing flexibility. You can see for yourself how the barbicels work by "zipping" together a feather by running a split section between your thumb and finger.  A major part of a bird's preening activities is just this feather fixing.

Because they can fly, birds do not need the camouflage of most terrestrial animals, and many are brightly colored.  The colors arrive from various pigments, the most common is melanin. This pigment is associated with keratin and provides some strength. Melanin gives a dark coloration and this is why the wing tips of some birds are black, to provide protection to the part that is most taxed in flight.

Carotenoids produce the reds and yellows we see in birds, but are not naturally produced in the body.  This pigment is produced in the liver and transported to the feathers when a bird eats bright red berries. Without that diet the Northern Cardinal, for instance, would not be its vibrantly colored self.

The pinks, browns, reds, and greens are produced by porphyrin, which is manufactured in the bird's body. Interestingly, the color blue does not occur in a bird's feather. Blue birds and jays, for example, are blue because — and get this —  "in the spongy nanostructure of the feather, the matrix between keratin and microscopic air cavities scatters light waves in an orderly fashion, sending only the color blue to the observer."  The same is true for the iridescent throat of a male hummingbird or the tail of a peacock — it is structural color, not pigmentation.

Spongy nanostructure or not, I still admire the beautiful blues of our Western Scrub Jays, and the gleaming throat of a Rufous Hummingbird. From its incredible strength and functionality, to its intense beauty, the feather is truly a marvel of evolution.

All content copyright Slo Coast Journal and Mike Stiles. Do not use without express written permission.
Burrowing Owl on Banner by Cleve Nash