Some feathers are as fluffy as that in their whole length.

Such are called down-feathers, because they are so downy.

Birds that run about as soon as they are hatched are always clothed in down, like little chickens, before their other feathers sprout; and some birds, like Ducks, wear a warm underclothing of down their whole lives.

Then again some feathers do not have any webs at all--only a slender shaft, as fine as a hair." "Do feathers keep on growing all the time, like my hair ?" asked Dodo.
"No, my dear.

They stop growing as soon as they are of the right size; and you will find your hair will do the same, when it is long enough--though that won't be for a good many years yet, little girl.
When the blood that has fed the growing feather is all dried up, the feather ceases to grow.