Papillomatosis - This is a sickness that causes pink wart like cauliflower growths in the oral cavities of the bird. This of course can cause the bird to eventually suffocate if left untreated. This illness is spread through preening and any close contact with other birds that may provide the potential for spreading the sickness. Signs include open mouth breathing, weezing, and an extreme difficulty while eating. This is most common to birds found in Southern and Central America.
Psittacosis - is a zoonotic infectious disease caused by a bacterium called Chlamydophila psittaci (formerly Chlamydia psittaci) and contracted not only from parrots, such as macaws, cockatiels and budgerigars, but also from pigeons, sparrows, ducks, hens, gulls and many other species of bird. The incidence of infection in canaries and finches is believed to be lower than in psittacine birds. This can cause your bird to show a decrease of appetite, constant diarrhea, mucus forming around the eyes, lethargy, weightloss, and noticeable depression in your bird.
Polyfollicles, Polyfolliculitis - This results in the development of multiple feathers from a single shaft. When this happens, it could cause a great deal of regular inflamation in the bird. This obviously could cause your bird a lot of pain and will result in regular scratching with the claws. It is important to watch closing to ensure that your bird doesn't cut themselves deeply with their claws while scratching.
Brown Hypertrophy - This is where the area containing the nostrils of the bird, the Cere, is cornified and keratinized. This could potentially create a horn looking appearance on the bird over time. a condition in birds especially budgerigars, less commonly other psittacines, characterized by hyperplasia, cornification and keratinization of the cere. It may occlude the nares and cause beak breathing.
Feather Cysts is a condition that can affect all bird species, and causes of a swollen, painful lump at the site of an affected feather follicle. Birds that are affected by feather cysts are in need of prompt veterinary care to correct the problem.