When Kipling wrote "east is east, and west is west, and never the twain shall meet", he could easily have been describing the distribution of some of Australia's birds. For thousands of years the Nullarbor Plain has acted as a barrier to many species which once spanned the continent before the climate changed, leaving populations of the same species isolated from one another. A good example of this is the Regent Parrot, which has two separate populations, one in the Mallee regions of eastern Australia, and the other in the Wheatbelt region of southern Western Australia. Though the populations are widely separated, the birds of each region do not appear especially different: Regent Parrots in Western Australia are merely slightly duller than their eastern relatives, having a slightly green tinge where the eastern birds are bright yellow. There are, however, other major differences between the two populations, especially in how they have fared: eastern populations are endangered, while the western population is thought to be increasing.
With the establishment of grain crops in Western Australia, the population of Regent Parrots quickly increased, and the species was considered a pest by farmers. They were declared vermin in many areas in the 1930s and 1940s, and many were shot during open seasons. This caused some populations to decline, but since they were removed from the vermin list, their numbers may have increased again. They are not considered threatened.
This contrasts with the population in eastern Australia, where Regent Parrots have not benefited from habitat change, and are considered endangered. Fragmentation of their habitat has resulted in hollow-bearing trees in which they nest becoming too widely separated from suitable foraging sites. Some birds may fly up to 20 kilometres between breeding and feeding sites, but recent clearance of mallee feeding habitat and logging of River Red Gums have made the distances too great to travel.
The accompanying map shows the two distinct populations of Regent Parrots, which are separated by the inhospitable habitats on the Nullarbor Plain and Eyre Peninsula.
If you want to discover more information about this species or any other birds that occur in Australia, just follow this link and you can explore BirdLife Australia's Atlas of Australian Birds.