“Whatever is causing the deaths is not giving us very much indication at all,” Mr Fitzgerald said. He said despite the thousands of carcasses, specimens suitable for autopsy were rare because the birds’ internal organs decayed soon after death.

Originally posted by mensmentis
I haven't found anything that says they know for sure yet. Per a news article originally posted previously in this thread (on page 5 by Wolfpack 51) they're having problems getting good specimens to test:

“Whatever is causing the deaths is not giving us very much indication at all,” Mr Fitzgerald said. He said despite the thousands of carcasses, specimens suitable for autopsy were rare because the birds’ internal organs decayed soon after death.

Originally posted by mensmentis
Yes - the organ decay is what caught my eye. First thought that came to mind was a bird sort of ebola. H5N1 generally doesn't have severe symptoms in wild birds.

Influenza A/H5N1 is "highly pathogenic", causing a severe disease with virtually 100% mortality in domestic poultry. The disease can be carried without symptoms in wild birds.

So I wonder if it is another kind of flu or perhaps a mutated form of H5N1 - found this on the WHO website:

First identified in Italy in 1878, highly pathogenic avian influenza is characterized by sudden onset of severe disease, rapid contagion, and a mortality rate that can approach 100% within 48 hours. In this form of the disease, the virus not only affects the respiratory tract, as in the mild form, but also invades multiple organs and tissues. The resulting massive internal haemorrhaging has earned it the lay name of “chicken Ebola”.

Originally posted by Regenmacher
Looks like they ruled out bird flu, so what's the chance that these birds died from EM radiation?

Wednesday, January 10, 2007. 3:18pm (AEDT)
Toxin blamed for 5,000 bird deaths in Esperance
A mystery toxin is believed to be responsible for killing an estimated 5,000 birds in Western Australia's Esperance region.
...
The Department says autopsy results point towards a toxin rather than bacterial virus. Mr Fitzgerald says both natural and man-made toxic causes are being investigated.

Australia : WA : Kalgoorlie
Thursday, 18 January 2007. 10:34 (AWDT)
Residents urged to contact DEC over dead bird discoveries
People who come across large numbers of dead birds are being urged to contact the Department of Environment and Conservation (DEC) as soon as possible. DEC scientists are still trying to work out what has caused the deaths of up to 4,000 birds around Esperance in recent weeks. They are also investigating the deaths of 200 swallows at Narembeen earlier this month. Paul Connolly from the DEC's nature protection branch says clusters of dead birds should be reported immediately so tests can be done to determine the cause of death. Mr Connolly says the DEC was unable to get a sample suitable for testing from the Narembeen birds because it was not notified in time. "The resident there had to go on holidays and was disposing of the carcasses soon after their deaths down at the local tip," he said. "So by the time we got involved the carcasses were well and truly starting to decompose."