butt feather loss

by sylvia
(New York)

I noticed about a month ago that my 21/2year old parakeet has lost his feathers around his butt and they have not grown back. I do not see any unusual picking of feathers in that area but my bird is particularly sexually active in that he masturbates several times a day on my hand. Should I be concerned about his loss of feathers?

Also, after ejaculation the parakeet vomits up some seeds which he later consumes. What is the reason for this?