Australasian Science: Australia's authority on science since 1938

Looking after Our Nomadic Species

By Claire Runge

The range of many Australian nomadic birds can contract to a very small area, making them much more vulnerable to extinction.

The full text of this article can be purchased from Informit.

Geographic range is often treated as a fixed attribute of a species when calculating extinction risk, with species occupying smaller geographic ranges assumed to have a higher risk of extinction.

However, many species move around the landscape. Migratory species move in relatively predictable to-and-fro migrations, while nomadic species move in complex and irregular movements.

We recently modelled the distributions of many Australian nomadic bird species, and found that at certain times their range contracts to a very small area, making them much more vulnerable than had been previously realised. This has important implications for how we calculate their risk of extinction.

Nomads move in complex patterns that are often associated with highly fluctuating resources, such as seasonal fruiting or irregular desert rainfall. Their movement strategies can be adjusted dynamically according to the prevailing conditions at each time and place. Australian bird nomads include the enigmatic and threatened grey falcon (Falco hypoleucos); the flock bronzewing (Phaps histrionica), which irrupts in incredible flocks of tens of thousands of birds in the outback; and the princess parrot (Polytelis alexandrae), a rarely seen but spectacular inland bird.

For many of these species we have only a rudimentary understanding of where they spend their time, when and...

The full text of this article can be purchased from Informit.