Bird poisoning source remains mystery

The source of a pesticide responsible for the deaths of hundreds of native parrots near Dubbo in NSW looks likely to remain a mystery.

As many as 700 mostly little corellas, sulphur-crested cockatoos and galahs were killed in the Troy Reserve area earlier this month.

Environment Protection Authority (EPA) testing carried out on carcasses identified the pesticide Fenthion as the likely cause.

The director of the NSW EPA's north branch, Gary Davey, says it's likely the improper use of the pesticide lead to the deaths but investigations had failed to find the source.

"At this stage we have no further leads to pursue," he said in a statement.

"This is very disappointing, given the number of native birds that were killed or affected."

The EPA inspected more than 20 sites as part of the investigation.

Mr Davey said it is important the community reported any suspected misuse of pesticides.

Additional bird and chemical samples had been sent for testing and any resulting evidence would be followed up, he said.

Prosecutions for misusing pesticides carry a maximum fine of $22,000 for individuals and $44,000 for corporations.