Every once in a while, a popular bird species kept in captivity is released by pet owners or escapes. They become successful, start nesting and producing young, and become established as a feral population in the wild. The English settlers, for instance, released house sparrows, European starlings and rock doves (city pigeons), all now firmly established across the country.
In more modern times, parrots, parakeets, bulbuls, mynas and other species have established themselves in several Texas cities and areas. Here on the upper Texas coast, for instance, we can find beautiful green monk parakeets, natives to South America, and they are expanding.