The WA government should stop logging immediately in old growth forest in order to save the lives of black cockatoos.

That's the opinion of Glenn Dewhurst, chair of the Black Cockatoo Preservation Society Australia.

Cockatoo numbers of both white-tailed and red-tailed species are decreasing in the South West and the metropolitan area, he says, and lack of food is one of the reasons.

Marri, jarrah nuts, hakea and banksia form part of the bird's normal diet, explains Glenn, "Unfortunately it is becoming more scarce."

Glenn, who is also Chair of Wildlife Australia, has been looking after injured birds since 2004. "(We would) get up to 300, 400 rescues a year," he says. "We have 200 at the moment."

"The birds used to come in at 640-680g, now we're getting them coming in at 480-500g." That amounts to a loss of a quarter of their weight, he says. Birds are weighed as a matter of course at the rescue centres and the society has ten years of data to call on.

Lack of feed, spring burning by the Department of Environment and Conservation and an aging population are all factors contributing to the number decline, says Glenn.

Spring burns kill chicks in the nest, he claims.

Maureen Griffiths with one of her charges. Photo: Chris Phillips

"A lot of people point the finger at farmers," says Glenn. "We've been following cases where DEC successfully charged farmers (over illegal) clearing. "But when you have a look at it, the areas they want to clear are not good cocky, or even native (species), habitat.

Farmers would plant more trees than they cleared which would be a boon to the black cockatoos, he says.

White-tailed or Carnaby's cockatoos are present southwest of a line from Eaneabba to Esperance, says Glenn while their red-tailed cousins occur between Albany and Perth.

The birds are heading for the Swan Coastal Plain in their search for food. However, says Glenn, the food is not available in these areas either.

"They're getting as far as Mandurah and dying. It's a march to the death."

Compounding the problem is that birds are also eating foods they would normally avoid and are dying as a result, says Glenn, foods such as unripe almonds.

"We can lose whole flocks." The society has had reports of up to 15 birds in a flock dying in backyards through eating the unripe nuts.

Cris Phillips of the Black Cockatoo Preservation Society. Photo: Chris Phillips

With enough alternative food, the birds don't eat normally feed on green nuts, says Glenn."We've thrown green and ripe almonds into our aviaries just to test our theory here and they won't touch the green almonds."

"But the fact is that they're so desperate for food that that's what they're doing."

He adds, "They're even eating jacaranda trees now; they're eating the seed pods of the jacaranda trees...Something they're never done."

The WA government has set up the Carnaby recovery program, notes Glenn, under which a population decrease of 10 per cent was deemed as failure.

The government hasn't released the count for the last 12 months, he says. "But (society members) have been telling us that we've lost between 30 and 50 per cent in 12 months.

"What the government needs to do is to stop logging in old growth."