Re: How do feathers grow?
Date: Fri Apr 3 10:17:03 1998
Posted By: Joseph Agro, SME from AT and T
Area of science: General Biology
There were a few different answers that I was able to come up with through
some of my contacts... I have listed them in the order of complexity and
what I think is probably correct.
Here's answer #1 and I think it is the closest thing to a proper answer:
Check out http://www.mindspring.com/~mi
"molt A process in arthropods, such as crustaceans and insects, as well as
in some vertebrates, such as snakes, whereby the organism sheds its outer
exoskeleton or skin periodically as it grows. Also refers to changing the
pelage or feathers in a mammal or bird."
"Most birds molt, or replace, their flight feathers once a year; some do it
more often. The alternating bands of lightly pigmented and heavily
pigmented feather material are laid down while each feather is growing--a
process that usually takes two to four weeks. The new feathers sprout from
follicles in the skin, somewhat like human hair. But whereas hair keeps
growing almost indefinitely, feathers grow until they are fully formed,
then stop. The blood supply to the follicle cuts off, and the feather
maintains its form until the next molting cycle."
"There are two categories of feather quality: Hard and Soft. Hard feathered
birds have tight plumage and bright colors. Soft feathered canaries have
downier plumage and the colors are subdued. In general, a Soft feathered
bird should always be mated to a Hard feathered bird. If Soft feathered
birds are bred together for a number of generations, feather lumps will
begin to appear. Feather lumps are unsightly masses of ingrown feathers.
The Gloster canary, the best examples of which are all Soft feathered, is
especially prone to this malady of genetic origin."
"I'm sure they happen in nature, but broken blood feathers are probably
more of a malady of domestic parrots whose flight feathers have been
clipped. A blood feather is a new feather that is still developing, and
which still has a supply of blood flowing into it. We usually notice them
if they are wing or tail feathers, since those are bigger feathers with
more potential for bleeding a lot! Feathers grow out of a follicle (just
like do our hairs). Each new feather starts out as a little bud inside the
follicle. As it grows, it will bump the older feather out of the way, and
this other feather will fall off. The new feather grows in a telescoping
fashion: the tip develops first, and it emerges well before the rest of the
feather is built. A constant blood supply is necessary to transport the
"building materials" to the growing feather. Once the feather is fully
developed and unfurled, it stays attached to the rest of the bird by a
"root" within the follicle. [...] People often ask 'well, if broken blood
feathers are so dangerous, why don't birds bleed to death in the wild, all
the time?!' The answer is in part that, since not all wing (or tail)
feathers get molted at once, each new feather is in effect protected while
it grows by flanking feathers. In a clipped bird, the new feather is
exposed; as such, it has a better chance of getting damaged."
So it looks like the answers are:
When birds molt, do feathers grow back in the follicle where they came from?
Yes. The new feather bud pushes out the old feather.
If so, how do they keep about the same number of tail feathers all of the time?
Only a small number of feathers are molting at any one time.
How do feathers grow? Do they grow in length first then fan out? We keep seeing
stick-like things coming out of our bird? Are those new feathers?
Yes. The feather "tip" develops first, then the rest of the feather grows.
The second answer I received was:
Feathers are like zippers in their construction. That's why when
you rub the feather the wrong way, it looks all dilapidated. The bird
straightens the individual parts of the feather with it's beak so that it
closes the gaps and hinges itself (like the zipper) so that it stays
together for flight. ta-da!!!
Birds are actually miniature flying Porcupines.... In truth, the feather as
such should never lose it's quill-like quality, but because they don't have
modern day conveniences like Prell shampoo when they drop by the birdbath,
their quills get split ends, and continue to fray out until they become
what we know now to be Feathers.
As for the Tail Feathers, a bird's tail is most important both for flight
navigation and for balance while perching. (You'd need a tail like that too
if all you had to stand on were a pair of coffee-stirrers)
The number of actual tail feathers never stays constant, as they must be
shed as well. there are at least two layers of feathers for the tail to
help ensure a solid 'fan' for guiding flight. when a feather is lost, it
won't seriously effect the flying porcupine's performance, except in the
case of attempted barrel-rolls and stunt flying to avoid cats....
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