Dr Denise Morgan will be undertaking the count over February 20-23. While they were noticeable in Yass in January and February last year, flying foxes have hardly been seen this year, she said.

"There were thousands of grey-headed flying foxes in the riverside area in [summer] 2018," she said. "It was a temporary camp. They will not form a permanent camp here because it gets too cold during the winter."

The grey-headed flying fox is listed as a threatened species. "The count will help us determine where they are and what's happened to them," Dr Morgan said. "They are important pollinators and we can't lose them."

Dr Morgan recently rescued a grey-headed flying fox trapped in netting near the Yass golf course. "The juvenile male grey-headed flying fox must have been around four months old. Due to overheating, it later died," Dr Morgan said. "We don't know how long it was in the sun. It was quite agitated, which led to overheating."

This was the first call for a flying fox rescue this year. In 2018, several calls were made in Murrumbateman and Yass. The count of flying fox numbers is underway across NSW as part of a census of the National Flying Fox Monitoring Program," a spokesperson for Planning, Industry and Environment said.

"This is a national program led by the CSIRO. The Department ... coordinates the count in NSW, undertaken by the state government and council staff, wildlife rehabilitators and other volunteers."