Grey-headed Flying Foxes to be precise. All 3605 of them, according to the Hunters Hill Council newsletter (June 2014).
It appears this colony, or ‘camp’, has relocated from the Sydney Botanic Gardens, possibly after dispersal efforts. In doing so they have created their own little “Mordor” – an ugly deadened hole in the foliage among some native bushland.
As noisy, destructive and smelly as they are, the Grey-headed Flying Fox is listed as an threatened species with a possibility of extinction. Until a Plan of Management is enforced, these Flying Foxes can call Riverglades Reserve their home.
Considering that’s an act of state government, I’d say they can afford to get cosy.