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. Pin feathers are therefore sensitive, and some pet birds do not enjoy being handled while moulting for this reason.
To stop bleeding from a pin feather, it is necessary to pluck the feather from its base. This can be difficult for a pet bird owner to do on a larger bird, so it is recommended owners have the necessary tools on hand in a first aid kit. The bird should be brought to a vet for assistance.
As the pin feather grows longer, the blood supply is concentrated in only the base of the shaft, and the tip of the shaft encases the feather itself, in a waxy coating. As moulting birds preen, they remove the waxy coating, and the feather unfurls.
When the blood has receded, the term "blood feather" is no longer synonymous with "pin feather" -- it can only be referred to as a pin feather.