Introduced Or Not?

I was drawing up a list of Tasmanian Birds recently, using a number of sources, and I came upon a dilemma. What constitutes an introduced species? Some sources included the Laughing Kookaburra and Corellas as introduced, others as, presumably, 'self introduced', across Bass Strait, and therefore acceptable 'Tasmanian' species. The Galah is known to have been introduced accidentally into the Huon area from a ship, in 1922. Perhaps those are the antecedents of birds that were frequently seen in the Kingston area for many years. However, the numbers now regularly seen around the State, would, I suspect, more likely be the progeny of birds having made the crossing from the Mainland. Nowadays, there are substantial flocks in many outer suburbs of Hobart, totaling some hundreds of birds. The Kookaburra, on the other hand, was known to have been introduced into the North and North East in the early part of the 20th century, and has gradually spread through the Island. Perversely, it is rarely listed as an introduced species. Perhaps it doesn't really matter except to the 'purist', and in many cases the question of the method of introduction of Mainland species, would be difficult to prove. The accompanying image of a Galah, was taken recently in the grounds of Clarence High School, Bellerive, one of the local flock numbering over 50 birds.