Australia: The Land Where Time Began

A biography of the Australian continent 

The Erratic Climate and Aquatic Birds in the Outback

One of the unusual consequences of the erratic Australian climate is that floods occur occasionally but not at predictable times in the arid lands, usually not from rain in the area but because enough water has been dumped in a short time outside the arid area and finds its way along the normally dry rivers of creeks that head inland where their water occasionally reaches places like Lake Eyre, but more often evaporates of soaks into the parched earth.

Many aquatic birds, both Australian and migratory, that normally inhabit the waterways near the coast gather at short notice when these floods occur or when ephemeral lakes form. The water of these lakes is often highly productive, more so than the coastal waterways where the water birds normally live, because the years of accumulating nutrients cause the rapid development of the food chains that only exist for short periods when the water is present.

Pelican Opportunistic Breeding

One example of this is when huge flocks of pelicans gather for an explosive burst of opportunistic breeding while the food is available in such large quantities. Such colonies have been observed to continue breeding while the food remains abundant, but by the time beds of aquatic grass begin to flourish the food for the pelicans has passed its peak and many of the young pelicans begin to starve to death. Then the black swans move in a begin breeding because they feed on the aquatic grass. Being a desert area there is a lack of normal nesting material so the swans use the bodies of the dead pelicans for nesting material.

Birds wait at the Flood Front

Another example of how Australian birds have evolved to cope with the erratic climate is the arrival of waders at the leading edge of the flood, which at this point moves fairly slowly, especially as much of the water is soaking into the dry ground and the desert sun is evaporating large amounts of water. As the flood front approaches, spiders and insects, and even small mammals like marsupial mice, are flushed from their burrows and are easy prey for the waders which have been waiting for them to emerge.

It is not yet known how the birds know when these rare and erratic events are about to occur. It has been noticed by duck hunters on the east coast that when the water birds are scarce there is usually flooding in the arid interior of the continent. How do the birds know where good breeding conditions have occurred in the desert and how do the waders know where to wait?

See also Yilgarn Craton

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                                                                                           Author: M.H.Monroe  Email:     Sources & Further reading