If you pull the tail feathers out they will grow back right away and you will see if they grow back white again. If you wait for him to moult, it could take six months you will probably be using him and breeding him and be six months down a bad road, lots of time and effort on a bunch of birds with traits that you didn't want, and no one else wants. Just grab a hold and yank quick. Hold tight, and snatch it quick. Just pull one to get the hang of it.