How chicken feathers grow

Unlike hair, full-formed
feathers can’t grow.  Instead, new feathers develop inside pointy
sheaths (at which point they are commonly called pin feathers) a bit
like a chicken develops inside an egg.  When the sheath comes off,
the feather will never grow again.



I start to notice pin
feathers on our birds about a week after feathers on the ground signal
the onset of our
chicken’s annual molt. 
In fact, the pin feathers were present all along, and their growth is
what pushed last year’s feathers out of the way.



The photo to the right
snows some pin feathers on one of our hens’ backs.  Younger pin
feathers near the top of the picture are still developing, but once the
feathers are fully formed, the tops of the sheaths turn white and begin
to flake off.  At the bottom of the photo, you can see pin
feathers with the new feather sticking out the top — within a few
days, these feathers will be disinterred and will start making our
flock look spiffy again.