Morana

Hello. I have an 8 year old affrican grey and about a year and a half ago he started to have a spot or two on his feathers. I wasn't concern until 8 months ago because I thought it was limescale from the bathing. However, 8 months ago it started to occur faster and since then the spots are progressing rapidly covering more of his feathers. First it appeared on the longest feathers on his back and now it starting to go towards his head. I allready spoke to our veterinarian, and brought a feather for analysis and she said there were no parasites, no bacteria or virus and under the microscope the spots look like holes. The feather is healthy except from this holes. She doesn't know what it is and it appears it is not affecting his health but it certainly doesn't look normal. I am extremely worried and I have no idea where to turn any more. I can't figure out what is causing this and why is it spreading more and more. I thought maby he was slowly poisoning himself with something which I am not aware of. Please help and thank's for any help.

This is Zak. He is a 8 years old and likes shreddable toys:-)