Most broken blood feathers are fairly easy to identify, as you will be able to see the blood coming directly out of the feather shaft. (thesprucepets.com)
A broken blood feather that remains in a bird's skin essentially acts as an open faucet, allowing blood to pour out of the bird's body. (thesprucepets.com)
Small pinfeathers on the head and body are not likely to cause any issues, but if a large blood feather in the tail or on the outside of the wing is broken, it can cause a bird to bleed to death fairly quickly. (petbusiness.com)