Around 300 corellas have been found dead in Horsham, Victoria, in a suspected mass poisoning incident near the Wimmera River.
The death toll has risen sharply since last week, when over 50 birds were initially discovered.
Horsham Rural City Council crews have been removing bird carcasses from the river and surrounding areas.
During the cleanup, crews discovered grain believed to be laced with poison, which has since been removed and covered to prevent further wildlife harm.
The Victorian conservation regulator is investigating the incident and has taken samples to determine the exact cause of death and type of poison used.
Authorities remind the public that corellas are a protected species, and poisoning wildlife is illegal and punishable by severe penalties, including jail time.
Conservation regulator chief Kate Gavens has urged the public to report any information that could help identify those responsible.
Residents are advised not to touch dead or sick birds but to document sightings and report clusters of five or more to the Department of Energy, Environment and Climate Action.
Anyone with information, CCTV footage, or observations of suspicious activity near the Wimmera River is urged to contact Crime Stoppers.
