At least 13 bats leaving hollow between 8.25 pm and 8.30 pm. Observed on other nights as well. Photo is a composite of frames from a short video, as it was too difficult to get photos. Many thanks to Ben Appleton.
Great photo, the profile looks like Wattled bats (Chalinolobus spp) , -most likely Gould's wattled bats, but its not really possible to ID from the photo.
Thanks Mike - when you lent us the bat recorder we picked up 5 bat species on Red Hill of which Gould's wattled Bat was both the most abundant and widespread species.