I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. Please let me know if you still need help. May I have an update on Pepito, please?
A bird that bobs its head up and down in a sort of pumping motion, beak open and then a purposeful delivery of partially digested food is regurgitating. This is something they would do to feed offspring or a mate. It’s done by some birds to objects (toys, mirrors, people) they are particularly fond of - especially if they’re in a breeding season, when a bird wants to please their owner and/or is of a nervous temperament. Regurgitation that is unusual enough for you to make note of it like you have, might be a symptom of crop infection/impaction and a bird losing ingesta in that manner will become malnourished.
Vomiting is more of a head “flicking” event. The bird will often seem uneasy, pacing or uncomfortable and although the head bobbing might be similar to the regurgitation action, it’s usually more of a shaking and the end result is a very splattered, sticky substance that may or may not include food. When there’s blood showing in the vomitus it may indicate esophageal or proventricular ulcers.
An avian vet (please see here: www.aav.org) will take a look into your bird’s mouth as part of a thorough physical examination and is likely to examine a swab of the oral cavity for abnormal numbers of either bacteria, yeast, or parasites. A good exam will also check for any growths or tumors.
Vomiting is a more serious symptom and seeing an avian vet as soon as possible is important.
There are far too many possible etiologies of vomiting to list in this venue, but as in any case of illness, getting it evaluated, diagnosed and treated right away is often the best outcome at the lowest cost. This isn't something you treat at home.
Gram negative bacteria are a common cause of gastrointestinal infection. These bacteria can proliferate after a bird is stressed. Stress can involve changes in their environment, being frightened, having their sleep hours reduced or other changes in schedules or even a difference in food. Another possible cause is contamination of food or water by fecal matter.
If your bird won't drink and eat on its own please consider eyedroppering an infant fluid and electrolyte replacer such as Pedialyte every 20-30 minutes. Put the dropper gently inside the beak and let the drops fall into the bottom beak under the tongue rather than trying to get into the back of the throat. We don’t want to chance of Pepito inhaling the fluid and developing pneumonia. Please heat up his environment to 85F so he need not expend excess energy keeping his body temperature up.
A good bland feeding option at this time is to offer all natural, organic baby food (squash, yams, sweet potatoes, mixed vegetables) which many birds take readily; also try some pablum or baby rice cereal and live-culture yogurt.
Please respond with further questions or concerns if you wish.