Since you only have one bird I can't see how he'd get mites or
anything like that, esp. in Dec.
I definately encourage you to see an Avian vet ( just to be
safe ). Because reg vets rarely have experiance in treating
birds ( other than nail & wing clippings & minor beak work ).
No telling what you've already paid this vet & for what? I
know that Avian vets are sometimes hard to find ( mine is a
100 mile drive one way ) & more expensive. But birds are
harder to treat, esp. since they hide their signs of illness
usually till it's really bad or even too late to do much for
One of the other posters mentioned stress bars & that maybe
the problem. Has anything ( at all ) changed in your birds
surroundings before Dec. ( new people coming over or other
pets being added to your home ), his cage being moved to
another room or getting a new cage? Does he have enough of the
right kind of light ( esp. during the winter months? What has
his diet been like? Only you can look back the past few months
& evaluate anything new ( no matter how small ). There is a
product called Red Palm Oil that helps condition birds
feathers that may help. But nothing suggested here is going to
be safer or better that a full check-up with a good Avian Vet!