Old friend (long-time friend?) Jim Greene of northern Virginia and Boone, NC commented in my previous posting that the bluejay has no blue pigments in its feathers. I had forgotten that feature of bird coloration, but a quick search of the internet located a number of references to structural coloration with some explanations of the bases for blues (and greens) in birds.
This short article by Anita Carpenter in Wisconsin Natural Resources gives the full story using layman’s terminology, and I recommend that you read it for a meaningful explanation. The experimental test of this explanation of structural coloration is easily carried out if you find a bluejay feather: the feather viewed in reflected light is blue, but if the feather is backlit and viewed by the light transmitted through the feather it appears brown!
Thanks, Jim, for offering this interesting observation.