A mystery illness is striking down birds across Perth, with experts no closer to knowing the cause.

Wildlife centres have been inundated with magpies, mudlarks, and ravens suffering from a form of paralysis that causes weakness in their legs and wings, poor responsiveness, and clenched feet leaving them unable to stand.

Helen Riley from Kanyana Wildlife Rehabilitation Centre in Lesmurdie said she had seen 14 cases in the past few months.

Only half survived.

"People have brought in magpies that seem to be weak, not able to fly up to the trees and perhaps other birds have been attacking them," Ms Riley said.

"We give them some fluids, possibly they need some pain relief that's also an anti-inflammatory. A lot of it is rest, warmth, fluids and a good diet to bring them back up to scratch.

"But some of them, if their immunity is compromised, they don't do well and deteriorate pretty rapidly and there have been a couple that we've had to euthanise."

She said a number of other wildlife centres were experiencing the same thing, with one in Bibra Lake reporting 60 cases of the mystery illness in recent months.

"We've just been talking to each other and found we've got the same symptoms," she said.

"We've been linking it together and saying 'OK, we might have something else happening, we need to investigate this further'."

Councils contacted amid fear of poisoning

Wildlife carer Barbara Wright examines a sick magpie at the Kanyana Wildlife Rehabilitation Centre. ( ABC News: Charlotte Hamlyn )

The Department of Primary Industries and Regional Development and Perth Zoo have carried out a series of tests but say it could be some time before they get concrete answers.

Perth Zoo senior vet Simone Vitali said the birds were presenting with symptoms similar to those reported in New South Wales where a neurological syndrome was blamed for mass bird deaths in between 2003 and 2006.

"There is a syndrome which affects birds in the eastern states," Dr Vitali said.

"Some of the cases so far examined in Perth have some parallels with this condition, but investigations are ongoing to determine if we are seeing a similar syndrome."

Local councils have also been contacted, with fears pesticides or fertilisers could be to blame, but Dr Vitali says there is no sign of that at this stage.

"Sick birds and dead birds have not been concentrated to a single geographical location and the findings so far do not point to a poisoning event," she said.

"Post-mortem examinations of bodies are being undertaken, with additional testing to investigate possible infectious causes for the deaths."

Staff at the Kanyana Wildlife Centre are asking members of the public to come to the aid of any birds, particularly magpies, that appear to be in distress.

"If they can catch it, wrap it up quietly, put it into a box, a nice dark spot so they feel safe," Helen Riley said.

"Bring it to us so we can do an assessment."