A pin feather, sometimes called a "blood feather", is a developing feather

Feather

Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

 on a bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

. 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. 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

Personal grooming

Personal grooming is the art of cleaning, grooming, and maintaining parts of the body. It is a species-typical behavior that is controlled by neural circuits in the brain.- In humans :...

, 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.