Cardeulis tristis
Auburn, Alabama
Note from Dr. Geoff Hill, Department of Biology, Auburn University:

"There seems to be no problem with the melanin pigments of this bird.
The wings and tail pigments look quite normal.
I think the lightness (of the head) comes from a depletion of carotenoid pigments.
We observed a similar pale feather coloration in House Finches when we left testosterone implants in the birds through molt.
So, whatever is going on with this bird, I’d say it is an effect on carotenoid pigmentation"