They contend this behaviour is a symptom of climate change and habitat loss, putting both animals and communities under strain. At Goulburn wetlands, about 1500 grey-headed flying foxes frequently colonise surrounding trees.

Nearly 200 kilometres further west, there are larger camps in urban areas in Cowra and Bathurst. New camps are popping up in the Upper Lachlan Shire. In November, an estimated 1000 animals took up residence at Markdale Station, a private property well-known for its extensive Edna Walling garden.

Experts say they were drawn to the area by a mass flowering of white box eucalyptus. The grey-headed flying fox is one of about three species of flying foxes that migrate around NSW' eastern coastal ranges, foraging for flowering eucalypt and nectar-rich plants and spreading pollen across the state.

Wildlife ecologist, Dr Peggy Eby says this vital migration of bats and flying foxes is crucial to the genetic diversity of native forests.

In February, she was the keynote speaker at Flight of the Flying Fox at Goulburn's Hume Conservatorium. It was part of a series of Land for Wildlife talks jointly run by K2W Link and supported through Cores, Corridors and Koalas - a partnership between the Great Eastern Ranges and WWF-Australia to restore and reconnect critical habitat for forest-dependent native animals.

Dr Eby tracks the animals from the south to the subtropical areas of northern NSW to collect information about the species' breeding season. She says a proportion of flying foxes have started changing their behaviours following a food shortage even after the event has ended.

"They continue to behave as though they were experiencing some sort of nutritional or metabolic stress," Dr Eby said.

"They are increasingly roosting in areas, where they didn't used to occur, and in areas that don't provide them with native fruit, and they have increased the number of roosts, particularly in urban areas. It is a really problematic wildlife management issue, and it's important, I think, for the people who live nearby to understand what's causing this. This is not a species whose population is exploding, this is a species under an enormous amount of pressure."

Increased plantings of nectar-rich trees and shrubs, like red gum, spotted gum, swamp mahogany and grey iron bark, can make a difference, Gary Howling, CEO of Great Eastern Ranges said.

"Flying-foxes rely on flowering species to get the energy-rich diet they need to survive. Unfortunately, these are the same ones that continue to be lost at a rapid rate leading to food bottlenecks occurring in winter and spring.

"By planting for pollinators, we can boost sources of food for flying-foxes during these leaner months, while also supporting the vital pollination services they provide and other local wildlife.

For more than a decade, Goulburn-based volunteer specialist bat rescuer Heather Caulfield has been rescuing, rehabilitating, and releasing bats back into the wild in the southern parts of NSW, from the Shoalhaven River to the Abercrombie ranges.

As flying foxes move into urban areas, Ms Caulfield and Dr Eby are working to raise awareness about bats' important role.

"People are concerned about their health or damage to trees and property, but the fact is the bats are there because of the flowering, and they are going to move on," she said.

"There's around 30 species of bat in NSW alone, and each species has its own environmental requirements and temperaments. They're so important to the environment. The more you learn, the more fascinating it becomes," Ms Caulfield said.