About four weeks ago I was startled to see this nearly bald blue jay at our feeder. It's possible that there were two such bald birds, actually, as it/they were quite a common site for a while, but I didn't see two together so I can't confirm that. I quickly learned that this is not an unusual phenomenon. I'd heard of it happening with cardinals, and it turns out it also happens with blue jays.
The Cornell Lab of Ornithology's Project FeederWatch page on bald birds notes that most such cases are reported in the summer and fall and may simply be a normal seasonal molt where the bird, for whatever reason, loses all the feathers on its head at the same time instead of gradually. Other causes may sometimes play a role -- perhaps mites, lice, or nutritional or environmental factors -- but the condition is not well understood.
The FeederWatch page cheerfully concludes, "Fortunately, new head feathers grow in within a few weeks." And indeed, this has been the case at our house. The birds we have seen recently are all properly feathered, handsome and sleek, like this one.
Have you seen bald birds at your feeders?