Hi, thanks for your question!
Flying-foxes are struggling at the moment to find enough food as a result of the drought and bushfires. As a result, many have been found deceased or acting unusually. You can read more about the north coast starvation event in our media release (https://www.clarenceconversations.com.au/flyingfoxes/news_feed/flying-foxes-fighting-for-food-after-bushfires). The starvation event could be one of the reasons why Maclean camp numbers are lower than normal.
Data from across the east coast suggests that starvation events and high heat events that result in the loss of large numbers of flying-foxes at a local level, don't have an ongoing impact on national numbers and the populations can recover quickly. The impact of the drought and bushfires this year has not yet been measured so time will tell. You can learn more about national numbers at the National Flying-fox Monitoring Viewer (http://www.environment.gov.au/webgis-framework/apps/ffc-wide/ffc-wide.jsf).
From historical events, we know that there can be a splintering of camps, with individuals moving elsewhere to access food resources. This can result in lower numbers at the main camps, so it could be that the flying-foxes that were consistently roosting in Maclean have also simply moved to other smaller camps or elsewhere outside of the Clarence Valley.
In addition, flying-foxes naturally move around in Australia over large distances. You can see the distribution of the species on the DPIE website (https://www.environment.nsw.gov.au/topics/animals-and-plants/native-animals/native-animal-facts/flying-foxes). Grey-headed flying-foxes are generally quite persistent at the Maclean camp. Black flying-foxes come and go but generally aren't around over winter, so should have returned just recently but numbers do seem to be lower than expected or arrival for the bulk of them is happening late. Little red flying-foxes are also not present at Maclean in winter and can generally can be seen in the Valley from late December to mid-March.
The Maclean flying-foxes used to spend significant amounts of time in the rainforest reserve and high school/TAFE, but now also use the gully more. Some individuals may have just moved up the gully, leaving fewer at the school.
So, apologies, but there's no clear answer. In summary, it could be a combination of the time of year and the widespread drought/fire issue resulting in lower numbers either at a local scale or overall. Time will tell.