The face was missing quite a few feathers. I looked into this and found that this is not uncommon for northern cardinals. However there appears to be a debate as to why this happens. The common theories are that it is a normal molting cycle for some particular birds, mites or other parasites, or other external influences such as diet or disease. Here is a close up of the face area.
No one really knows the cause because there has not been much research done on the subject but here are some links to more information.