Hi there, this is the Birdcare Company's web site.

The Birdcare Company, birdcare, health, nutrition and breeding advice for bird keepers. Budgerigars, canary, canaries, finch, finches, parrot, parrots, parakeet, parakeets, cockatoo, cockatoos, african grey, macaw, conure, pyrrhura, cockatiel, lovebi

They are really knowledgable with their products and are really easy to talk to. I would say that if you are really concerned about your bird then get him off to the vet for a check up. Birds try not to show signs of illness as it would put them in a vulnerable position to predators. Moulting is not usually classed as an illness in itself but can be a symptom of other illnesses. As for how long it lasts, I have found that it seems to depend on the bird. It can be a stressful time for birds so just keep him quiet until he appears to improve. I usually find an improvement within 24 to 48 hours of giving spark. Usually they moult twice a year, just before breeding and just following so you boy sounds like he is going through his moult to come into breeding condition. Hope this helps. Let me know how you get on.

Have no idea what has happened to the link as I posted but just click it, it does work.