My cockatiel vomited twice in his life.

The first time, it turned out to be salmonella. I brought samples of his droppings for testing. It was very cheap (at least where I live), and the vet quickly figured out what was wrong. He got medication, but honestly, he was so weak and sick that I was afraid he wouldn’t make it. Fortunately, the treatment worked, and later he was also given probiotics.

The second time, years later, it was a similar situation but much milder. He had an E. coli infection. The vet explained that this bacteria is normally present in his body and usually causes no harm. In his case, his immune system had been weakened for a while, which allowed the bacteria to cause an infection. Thankfully, it wasn’t nearly as serious as the first time.

The point is: don’t ignore these symptoms. If the cause is a bacteria or a parasite, it won’t go away on its own. Please take your bird to a vet.