Hello all, i have 2 birds that i recieved from friends in 2000, when fully grown my bird to seems to turned out fine and quiet plumply while my sisters seems to be very thin and still is. until recently my sisters bird began to lose feathers under the wings and now from the feet to it's upper chest and around the beak, most of the birds body is not covered by feathers. My sisters bird seems not not fly normally either. I keep the house warm so the bird won't die of being too cold. I feel ashamed and quite stupid for not taking the bird to the vet, can anybody tell me what my next step is to help my bird? Both birds eat the same food and eat normally also dropping seem to be normal.