Testing underway after mass bird death in country WA

Some 78 galahs, corellas and other birds were reported to have died in Coorow. (ABC Mid West and Wheatbelt: Jo Prendergast)

A wildlife carer says 78 birds have been found dead or dying at Coorow in WA's Wheatbelt.

Some locals believe the deaths are related to poisons spread to control mice, but the cause is yet to be determined.

The public is advised to report further sightings and avoid handling dead birds.

A wildlife carer in Western Australia's Wheatbelt says 78 birds have been found dead or dying in a local town, with the cause now under investigation.

Shannyn Bean, a wildlife carer in Coorow, around 260km north of Perth, said locals began finding the dead and dying birds on the town's oval and school grounds on Wednesday.

She said the birds, largely corellas and galahs, appeared normal when taken into care, only to rapidly deteriorate.

Ms Bean said she and her organisation, Bluebush Wildlife Rescue, had contacted WA's Department of Primary Industried and Regional Development (DPIRD) when the first dead birds were spotted.

"After coming into care they are dying, and we are unsure why," she said.

Corellas are classified as an invasive pest in WA and subject to organised culls.

Even so, Ms Bean said determining the cause of deaths was important to ensure vulnerable local species like the Carnaby's black cockatoo were not under threat.

Carnaby's black cockatoos forage on native trees and shrubs in the WA Wheatbelt. (Supplied: Rick Dawson)

"People have been speculating that it could be due to poisons. Because of the recent mouse plague, poisons have been utilised," she said.

"But we can't confirm that is the cause of what is going on."

The mystery bird deaths come as the region battles its worst mouse plague in living memory, forcing farmers to spread baits in a bid to reduce mice numbers.

Paddock-approved baits are grains of wheat containing zinc phosphide.

Last month, the pesticides regulator approved the use of double-strength baits on severely impacted farms.

Baiting is governed by strict guidelines, including rules about how and where baits can be spread.

The legal rate for application of zinc phosphide grains in paddocks is three grains per square metre.

CSIRO testing has so far found there is a low risk to birds from zinc phosphide baits if they are spread at the legal rate.

In March, the regulator banned the use of second generation anti-coagulant rodenticides for anyone other than licensed pest controllers, due to their impact on other wildlife.

Mouse bait spread on paddocks is wheat treated with poison. (ABC Mid West Wheatb