Why is the head and neck of the adult California condor largely bare of feathers?

Answer

To allow the bird to keep clean while feeding on carcasses

The lack of dense plumage on the head and neck is a functional adaptation that prevents feathers from becoming matted with blood or tissue deep inside large carcasses, reducing flight impedance and bacterial risk.

Why is the head and neck of the adult California condor largely bare of feathers?
birdappearanceanatomycharacteristiccondor