At least 100 ducks have been found dead at Bells Swamp in Central Victoria over the past week, a wildlife rescuer says.
Concerned locals raised the alarm and alerted authorities on Tuesday, after noticing several dead ducks in the nature conservation reserve at Neereman, south-west of Bendigo.
Local wildlife rescuer Sam, who wished to be known only by their first name, said they were initially concerned people were illegally hunting ducks.
"I just came down and checked it out. There's been approximately 100 birds I've pulled out over the last four or five days that have died," Sam said.
The local animal lover took a kayak out on Bells Swamp on Sunday, looking for sick ducks to rescue.
"I've retrieved six ducks in the last hour," Sam said.
Authorities confirmed at least 20 dead ducks were found on Wednesday.
Locals say many more have been found since.
Parks Victoria, the lead agency for Bells Swamp, has been inspecting the nature conservation reserve every day since Wednesday.
Wildlife Victoria vets were on site for the first time on Sunday and euthanased several animals.
People warned to stay away
Since residents first alerted authorities on Tuesday, a group of concerned locals have joined forces to try to save some ducks.
"Maybe we prevented it from becoming a more widespread event," Sam said.
Sam said they were able to rescue dozens of animals and had sent them to a Melbourne vet.
"At least 13 ducks have been saved so far."
Ducks have been tested to find out the cause of death, with the results expected in a few days.
Locals suspect avian botulism, only the test results can confirm the cause of death.
"The concern is that avian botulism can really affect thousands of waterbirds," Sam said.
Initial test results show no signs of human involvement, allaying concerns about illegal duck hunting.
Parks Victoria has put up signs warning of a potential health risk at Bells Swamp.
"We ask that people stay away from the reserve until further notice," a spokesperson said in a statement.
