Up to 60 birds have died in a suspected poisoning after "falling from the sky" covered in blood.

The birds - the majority of which were the protected long-billed corella - were found in South Australia on Wednesday as they fell out of trees and from the sky.

Some of the cockatoos, only three of which were the non-protected short-billed corella, were already dead when rescuers arrived at the sight.

Others were alive but had blood streaming out of their eyes and beaks.

They were taken to two veterinarians but of the 60-odd birds discovered at One Tree Hill, Adelaide, a staggering 58 died.

(Image: Facebook)

(Image: Facebook)

Casper's Bird Rescue founder Sarah King told the Guardian a staff member of hers who discovered the birds called her to say the white cockatoos were "literally falling out of the trees in front of him, falling out of the sky".

She described the scene as something straight out of a "horror movie".

"The birds weren't able to fly and were lying on the ground wailing in pain. Some birds were bleeding out of their mouth," she told the BBC.

(Image: Facebook)

"That immediately made us think of poisoning, which we've seen before."

Ms King believes the type of poison used inflicted a "horrific, slow death" which kept the birds in pain for weeks.

The species have previously been threatened with culling as they're considered destroyers of crops and street lights.

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The state's Department for Environment and Water told the broadcaster the cause for the poisoning is yet to be identified and that a disease and toxin testing is under way.

Those found guilty of harming protected species could be liable for a fine or even jail.