Red-tailed Black Cockatoos are the most widespread of all the black cockatoos in Australia. They occur from the driest regions of the inland right through to coastal forests in both eastern and western Australia.

There are four or five subspecies (depending on which book you refer to). The most specialised of these, a small form "naso" is restricted to forest regions of SW Western Australia where the food is almost exclusively seeds of various eucalypts. Known colloquially as "forest red-tails", future research may well prove them to be a separate species. A rather similar situation has arisen in far SW Victoria and adjacent SA where the now isolated and endangered subspecies "graptogyne", also essentially a forest-dwelling type, feeds largely on Red Stringybark, a species of eucalypt gradually disappearing because of the spread of commercial plantation timber.

Throughout the rest of Australia the remaining subspecies are fairly safe, particularly in northern Australia where flocks numbering thousands are sometimes seen. A wider choice of food may account for their success. I have seen birds in the towns of Gympie, Qld and Bourke, NSW feeding on the fruits of White Cedar. In the Townsville district they are partial to the fruit on the introduced Chinee Apple, (Ziziphus mauritiana) a widespread weed. Over in the wheatbelt of Western Australia, the introduced burr 'Double Gee" (Emex australis) a major weed of wheat crops has become the principal item in their diet in some areas and is even allowing a southerly expansion of their range where they now compete for nest holes with the endangered Carnaby's Black Cockatoo.