I have had a few reports recently of unfamiliar birds showing up at feeders. I have been seeing some unusual-looking birds too, which is normal for this time of summer.
Northern cardinals often will lose their head feathers in mid-summer, exposing the blue-gray skin. They actually go bald. The rest of the plumage is retained, giving the bird an appearance of a small turkey or turkey vulture. They do look sort of prehistoric. Feeder watchers often become concerned that the bird is ill, but apparently they are OK. They appear healthy otherwise and continue to have good appetites.
The feather loss may be due to a combination of factors, including feather mites and a disruption of the normal molting schedule. I have seen this condition in blue jays and common grackles too, and I suppose any species that goes through a fall molt could exhibit the characteristics.
Many times the reports of unusual summer feeder birds refer to young birds retaining their juvenile plumage. These plumages can in some cases be totally different from adult plumage. I recently did a double take myself when I looked out the window and saw an odd bird scratching the ground under the feeders. I quickly recognized it as a juvenile Eastern towhee in a plumage that looked nothing like its parents. The size, shape, and behavior all were consistent with Eastern towhee, however.
The juvenile red-bellied woodpeckers are not as brightly colored as adults either, but they retain the general plumage patterns. The same holds true for downy woodpeckers and northern cardinals. It’s not too hard to figure out what they are. If you are lucky enough to have indigo buntings as feeder birds, you may see the young birds visit eventually. They will be all brown with none of the brilliant blue of the adult males.
Learning and studying bird shapes and behaviors will help you with identifying the odd-plumaged common birds that might occur right now.