Blood feather:
1. Color: Blood feathers often appear darker or redder than the surrounding feathers due to the presence of blood in their quills.
2. Shaft: The shaft of a blood feather is usually darker and more opaque than the shafts of nearby feathers.
3. Tip: The tip of a blood feather may be broken, chipped, or frayed due to damage.
4. Bleeding: If the feather is pulled, it may bleed or ooze blood.
Primary feather:
1. Color: Primary feathers are usually the longest feathers on a cockatiel's wing and are evenly colored.
2. Shaft: The shaft of a primary feather is typically light-colored and translucent.
3. Tip: The tip of a primary feather is usually smooth and intact.
4. No bleeding: When pulled gently, a primary feather should not bleed or ooze any blood.
If you are not sure if a feather is a blood feather or a primary feather, it is best to consult an avian veterinarian for proper identification.