In
1989, following the inland floods, ten lakes in the Roxby Downs area
filled with water and the last of these didn't dry up until six years
later. Consequently, the arid inland of South Australia became a haven
for waterbirds ranging from all kinds of ducks to the largest pelican
colony ever documented.
Unfortunately
for these birds, the mining industry can be fraught with hazards and one
of these is the presence of the "tailings dams", huge plastic
lined ponds into which the leftover dirt and rock, suspended in water,
acid and other chemicals, is pumped. These ponds look relatively normal
to a waterbird, especially at night when they fly, and in the early
1990's a range of waterbirds took to roosting on these toxic ponds for
the day.
"Although
the tailings ponds were too acidic for the ducks to drink or to
sustain any aquatic life that they could eat, the tenacity with
which the birds clung to these stinking ponds at first defied
comprehension."
Luckily
although the lakes are highly acidic, veterinary analyses have shown
that if the birds are removed from the ponds within a few hours they
will usually survive. However, the birds seemed completely unmoved by
the sirens, horns, rock hurling and cursing by the despondent team of
human scarecrows that John mustered to remove them.
The
mystery of their stubborn refusal to leave the ponds was solved by one coot,
a black chook-like waterbird that actually responded to a rock thrown by
John, taking off from a pond in the middle of the day and rapidly
gaining height - until a wedge-tailed eagle, the world's fourth largest
eagle and an effective daytime predator, swiftly demonstrated why these
waterbirds only fly at night.
John
had taken up birdwatching in earnest by this time, and would amuse
himself at night while camped by one of the various lakes by playing a
torch beam across the surface of the lake. Wherever the light's beam
landed, scores of waterbirds would take to the sky in response. Eureka.
A
series of trials on various ponds showed that the DUCKOFF, along with
the use of gas guns, was indeed significantly reducing the numbers of
waterbirds recorded on the dams. Since then, other mines have adopted
similar methods and strategies in an effort to reduce waterfowl deaths
at their mines. Of course, the lakes have since dried up and the
waterbirds have moved on. But floods are an integral part of the outback
climate and someday they will be back...
"When
they do return a bank of rotating beacons rather than red-faced,
rock throwing biologists will confront them.
