My cousin has a budgie called chicken. He is all yellow with some white feathers here and there. I looked at a heap of sites to try and find out what type of budgie he is, but i have seen no others with no flight feathers or tail, and he has never had his wings clipped. He can't fly. He got him from a pet shop, they just said he was a yellow budgie.Theres a pic of him in my gallery if you know of any other budgies like him. My cousin thinks he's half canary but i doubt it. Oh, my cousins had him for a good 4 years and nothing's ever happened to him exept his wing started bleeding once or twice.
It sounds like your cousin's budgie could have french moult. I have no idea if this disease is harmful or not as I have never researched it. I do know that it can cause a budgie to lose tail feathers and flight feathers.
I agree with Kelsey (chompie_puppy). The budgie has French Moult. This is a disease that affects young budgies when they first leave the nest, some recover and grow normal feathers later and some remain "runners" all their lives. There is a lot of disagreement about the cause but affected birds usually are healthy in every other way and can live out a normal happy life as a pet. They should never be used for breeding and I think that it was irrresponsible of the pet shop to sell the bird without giving proper information
One theory is that it is passed in the egg, another says the germs can be found in dirty nest boxes, others claim that it is caused by vitamin and mineral deficiencys. There have been several studies done and each claims to have the answer but none are really conclusive. Adult budgies can't catch it