Biology Reference
In-Depth Information
CHAPTER
11
On Angels' Wings: Fascinating Feathers
We mammals are a varied class of animals coming in myriad shapes and sizes, from
bats to whales, giraffes to platypuses, lions to human beings. The tiniest shrews are of
similar size to hummingbirds, but the largest whales are orders of magnitude larger
than the biggest ostriches or even the most gigantic birds that ever lived, the moas
and elephant birds. All birds stand or perch on two feet, and although a few, like the
kiwi and ostrich, have only vestigial wings, the overall bird shape is distinctive.
Bird bodies are covered by and get their distinctive shape from feathers — a
unique feature found nowhere else in the animal kingdom. What mammal could truly
be called “resplendent” or “scintillant,” or be justifiably named for any of the gems
common in hummingbird names — ruby, amethyst, topaz, emerald, sapphire, or gar-
net?
Small wonder our depictions of angels portray them bearing the wings of birds.
And small wonder that when we see birds, our minds are filled with questions.
Fine Feathered Facts
Q What are feathers made of?
A
Feathers are features unique to and universally found in all species of birds. Each one
grows out of a specialized structure called a
papilla.
Human hair also grows out of papil-
lae — biologists are still researching how similar these structures may be, and how similar
feathers may be to reptilian scales. Compared to scales, feathers are much softer and more
flexible, are extremely lightweight but strong, and provide excellent insulation against ex-
cessive cold and heat.
Intuitively,itseemslikefeathersmusthavestartedoutasscalesthatevolvedtobecome
frayed.Butdevelopmentalbiologistspointoutthatfeathersbegingrowingastubularstruc-
tures quite different from scales. Scientists are still debating
why
feathers evolved —
whether they were originally for insulation, flight, display, or some other function. There
are lots of fossils that suggest many feathered dinosaurs did not fly.
Feathers are composed of phi-keratin, which is not known to occur in any nonbird animal
tissue except alligator claws.
