A large number of dead galahs have shown signs of possible poisoning after "literally falling out of the sky" in South Australia's Lower Lakes region.

Milang local and wildlife carer Sarah Hope said she first noticed a dead pink and grey galah in her backyard on November 27.

She told ABC Radio Adelaide that large numbers started turning up dead in the town and adjacent to Lake Alexandrina after clearly suffering a "horrific" end.

"A lot of people in the area, including those who come here for holidays, are distraught by seeing these animals literally falling out of the sky," Ms Hope said.

"It's absolutely horrific. They go down so fast and you can see how their claws are balled up because they can't hold onto the branch any more and fall out of the trees.

"They're literally face down on the ground."

Ms Hope sent two of the dead birds to Biosecurity SA which delivered a pathological report indicating a "significant congestion of organs, which commonly occurs with poisons/toxicity".

There were no signs of disease and the agency described it as a suspected poisoning involving 50 birds in the Milang area.

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Government testing for toxins

Ms Hope said more than 100 birds had since been found and she had delivered a further 20 for toxin and pesticide testing.

In a statement to the ABC, a Biosecurity SA spokesperson said the cause of the mortality did not appear to be an infectious disease.

"Testing for non-infectious causes such as toxins are now being conducted but may take several months for results to be available," the spokesperson said.

"Initial results may be available within the next four to six weeks."

An initial pathology report on two galahs found organ damage consistent with poisoning. ( Supplied: Sarah Hope )

Magpies and pigeons also affected

Ms Hope said she had since heard reports of galahs being found in Murray Bridge and at Goolwa, and hoped the Government took it further to test the environment and find out where the "chemicals were coming from".

She said in the past week the deaths had crossed species into magpies and pigeons, while a large bird of prey, possibly a wedge-tailed eagle, had been found in an advanced state of decomposition.

"It's face down and has died in the same way. It's really tragic."

She said corellas had just started to arrive in the region but that the galahs came first in larger numbers than usual.

"It seems they're coming down to the lake because it's so dry up north, but the first flock that came down has become nothing within a couple of weeks.

"I've held more birds as they've died in the past few weeks here than I have in 20 years as a wildlife carer."

Authorities will test for up to 200 chemicals in the birds' livers and a part of their digestive tract near the mouth called a crop.

Full results, however, could take up to three months.

Burra bird deaths remain unsolved

Earlier this year some 200 galahs were found dead in the town of Burra in the state's mid-north.

An investigation by the Department for Environment and Water was unable to find a cause of death.

At the time a spokeswoman said laboratory testing did not rule out a toxin or poison being involved.

She added that a criminal investigation had not been launched because galahs were not a protected species and could be killed without a permit.

Anyone wanting to report bird deaths in other locations should call the Murray Bridge Natural Resources Management office on 8532 9100.