Wee Jasper, bats and raptors

["Overs, Anthony (REPS)" <>]

Last Thursday evening I spent a couple of hours at Wee Jasper, assisting an old friend in the monitoring of a large bat colony right near town.

We stopped at the tavern for a steak sandwich for dinner, and while sitting outside I observed plenty of Yellow-rumped Thornbills, Galahs and Sulphur-crested Cockatoos in the tavern garden and surrounds. A Collared Sparrowhawk cruised over quite low, but no other birds seemed to care. Shortly after, an Australian Hobby flew over, a bit higher, and heading south with purpose.

The cave we were watching is one of only three known maternity colonies in NSW for the threatened Common Bent-wing Bat (Miniopterus schreibersii). In the past the cave has been home to up to 30,000 individuals. On Thursday night we estimated about 15,000, although my friend Doug has yet to count them on the thermal camera recording (apparently some software does it – he doesn’t sit there counting them one by one!). It’s some of the easiest field work I’ve ever done; 50 metre walk, set up the cameras, sit in a chair for an hour!

The bats began to leave the cave entrance (maybe a metre wide), just as the sun set behind the hills to the west. The light was still very good and the bats were easily observed. After about ten minutes from the first bat leaving, the rest followed in high numbers. It took about an hour for the whole lot to leave. An incredible sight, and also an amazing sound as the many sets of wings fight to get out of the small cave entrance. Some of the bats, presumably young ones just learning to fly properly, crash-landed in the grass occasionally, pausing for a moment then taking off again.

Now, many moons ago I heard of an instance of an Australian Hobby successfully hunting small bats at dusk. Has anyone observed this? As I sat next to the cave and watched the bats heading out into the woodlands I thought it would be such easy pickings for a fast manoeuvrable raptor like a hobby or sparrowhawk (amazingly the two species I’d seen an hour earlier at the tavern) to catch a bat or two for dinner. Maybe even a Boobook or Barking Owl might get in on the action. Any comments?

Cheers

Anthony