The consequences of this geological history are that the bird faunas of the Australo-Papuan islands share many common features and are mostly Australian in origin. Similarly the bird faunas of the Sundaic are Asian (oriental) in origin. The Wallacean islands have a hotchpotch of species derived ffrom both the oriental an Australian zoogeographical region but with many endemic forms which have evolved on the different ilands as a result of their long isolation.
The Sundaic islands of Borneo, Sumatra and Java together with the Malay Peninsula share about onto the Asian mainland nor cross to adjacent Wallacea and this gives the sundaic area sufficient zoogeographical distinction to be classed as a separate faunal sub-region.