Everytime this year, I make two related observations. First, the number of Google searches on "bald Blue Jays" skyrockets. Second, I start seeing bald Blue Jays in my yard.
Blue Jays go through one complete molt a year in late summer. This molt usually proceeds in an orderly fashion so that you barely notice that it's going on. But Blue Jays (as well as Northern Cardinals) often experience a complete molt of their head and maybe even their neck feathers. Nothing is wrong with the bird and the feathers will grow back.
But for a period of time until they feathers return, they do look rather odd. Get out a pair of binoculars and look for bald jays in your yard. Let me know if you see one.