Bird Vomiting
Unlike humans, vomiting can be a normal pan of a bird’s behaviour. For example, birds of prey vomit 
undigestible material such as bones. Budgerigars may vomit as part of their courtship behavior. However, vomiting may be a sign of a problem, especially if associated with lethargy, not eating and diarrhea and ingestion of foreign material.
Causes
- Moldy food.
- Infection.
- Crop injury and/or obstruction.
- Overeating.
- Poisoning.
- Kidney failure.
Signs
- While you may not observe the bird vomiting, an obvious sign is the matting of feathers around the birds head with what looks like a tacky mucus and partially suggested food or seed. Also, the vomit may be adhering to the interior of the cage.
Treatment
- Keep the bird warm, remove any food from the cage and make sure water is available.
- Take the bird to your veterinarian as the causes of vomiting are numerous and the diagnosis of some of the causes can only be made by pathology and/or X-ray.