The flying-fox camp in our Palmetum gardens seems to have become as permanent as flying-fox colonies ever are, having been occupied through the last months of 2012, vacant in December 2012-early 2013, but occupied continuously since then. Numbers fluctuated but were high by the middle of 2014 when the Bulletin grumbled about the “infestation”. By that time the flying foxes had acquired time-sharing co-residents: white ibis were nesting amongst them.
I saw the two species together at about that time and thought it was quite peculiar, but in fact it is not a new habit at all. They were doing it more than ten years ago in a mangrove forest near the mouth of Ross River:
The [Ibis and Egret breeding] colony [on the south bank of the Ross River] is dominated by a tall mixed-species mangrove forest, backed by saltcouch flats and saltmarshes. Several species breed within the colony at various times throughout the year. The Australian White Ibis (Threskiornis aethiopica [T. molucca]) and Straw-necked Ibis (Threskiornis spinicollis) are present throughout the year as are small numbers of Great Egret (Ardea alba), Intermediate Egret (Ardea intermedia) and Little Egret (Ardea garzetta). During summer, increasing numbers of Cattle Egret (Ardea ibis) visit the site to breed.
Flying-foxes co-inhabit the colony, in the form of a time-share: as the last birds return to roost, thousands of Black Flying-fox (Pteropus alecto) are heading towards their nocturnal feeding grounds. A seasonal Visitor is the Little Red Flying-fox (Pteropus scapulatus), a very nomadic species. Together these two species can add up to tens of thousands of Flying-foxes in the Ross Colony. …
The Ross flying-fox and ibis colony covers 45 hectares of mangrove forest dominated by Red (Rhizophorastylosa), Yellow (Cenopsaustra/is) and Grey Mangroves (Avicennia madna). The colony is used not only for roosting, but also for breeding for all species who inhabit it. This fact alone is a rare phenomenon. At peak breeding times, the White Ibis have been recorded in their thousands, and the Black Flying-fox and Little Red Flying-fox numbers can both climb into the tens of thousands. An unforgettable sight in the late afternoon is to see the ibis and egrets flocking back to their roosts, and the flying-foxes streaming off for the “night shift”.
The above comes from this pdf on the Townsville State of Environment Report – 2003 website, and the mangroves are those in the distance in this photo, across the river from the port. My friends over at Wildlife Queensland’s local branch suggest that in fact the flying foxes only took up residence in the Dan Gleeson Gardens and the Palmetum when the Ross River colony was disturbed by cyclone Yasi and the port access road-building work in early 2011, and that they have recently begun to return to their traditional home.
We will never know know which species occupied the mangroves first, or how long either species has been there, but I’m fairly sure the ibis moved in with the flying foxes, not the other way around, at the Palmetum. There have always been plenty of ibis in the park, usually around the lagoon, but I don’t remember them nesting in these rainforest trees (or anywhere else in the gardens) until after the flying foxes moved in.
My conversation with WQ about the movements of our flappy furry friends may lead to further posts about them, either here or on their branch blog. Meanwhile, read this article from Australian Wildlife for more about all Australian flying foxes; it’s long but it is very good and has some lovely photos.