Pin feather

A pin feather, sometimes called a "blood feather", is a developing feather on a bird. This feather can grow as a new feather during the bird's infancy, or grow to replace one from moulting.

The pin feather looks somewhat like a feather shaft. However, unlike a fully developed feather, the pin feather has a blood supply flowing through it. As such, if the pin feather is damaged, a bird can bleed heavily.