Carnaby’s black cockatoo in trouble
PESTILENCE, HEAT, AND STORMS of almost biblical proportions have plagued Western Australia’s most vulnerable parrots in recent years.
The confluence of events, including land-clearing, has led senior researchers of the Carnaby’s black cockatoo (Calyptorhynchus latirostris) to wonder if the endangered species can survive a future era of climate change.
This handsome bird with a plaintive ‘wee-lah’ cry once flew over Perth in cloud-like flocks of thousands. But now just catching site of one is a rare chance.
Strenuous conservation efforts are being made to reverse their decline. But veteran bird scientists Denis Saunders, Peter Mawson and Rick Dawson – who have collectively studied Carnaby’s black cockatoo for many decades – say a sequence of bizarre climatic events between October 2009 and March 2010 hint at other threats to survival.
Mysterious deaths
First, in late 2009, fifteen birds were found to have died of a mysterious, unidentified disease in their hollows at Koobabbie, in the northern Wheatbelt. Then in early 2010, severe thunderstorms and hail stones killed 81 birds across Perth’s suburbs. Further east, near the coastal town of Hopetoun, more than 200 adult birds were found dead in trees in the midst of a sweltering heat wave; local papers reported some birds as having “dropped dead from the sky” in temperatures reaching 50ºC.
“The birds are in trouble, not only from clearing of native vegetation, but also from extreme climate events,” says Denis Saunders, who co-authored the scientists’ recent paper for Pacific Conservation Biology.
The scientists found that after the puzzling disease outbreak, breeding birds had halved in number in one Wheatbelt region. The hailstorm deaths had reduced flocks of birds by up to 13 percent in Perth’s suburbs.
Elsewhere, heat stress had been catastrophic, they reported. “It was not limited to the 208 birds recovered…[it] may have also affected many chicks as a result of their parents being killed, if the chicks were not killed by the extreme heat.”
Nail in the coffin
The scientists say that if hail, heat and environmental disease are capable of such damage, climate change might be the final nail in the coffin for Carnaby’s Black Cockatoos.
Denis says he is compiling further data from his own field work, spanning 1969 to 2010, which shows that early autumn rainfall is crucial to the Carnaby’s egg-laying success.
“It is clear that there is a very strong correlation; the lighter the rainfall in the first half of autumn, the later the birds lay. The later they lay, the greater the impact of hot weather on those trying to rear young.”
If weather patterns become more extreme, more birds will die and their preferred woodland habitat will shrink as the arid zone moves closer to the coast.
Says Denis, “It all means that Carnaby’s Black Cockatoo is in deep trouble.”
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