could you use a torch?
Tawnys are a nice bright colour so in the dark will expose ok with some
light.
If you try a torch, just be weary of LEDs and how they can have massive colour inaccuracies(terrible CRI), so try to get a grey reference point of some type to colour balance it later. I find just a test shot and 'click to whitebalance' is usually good enough.
I have a fruitbat that comes every night to feed on a plum tree in my yard, and thinking doing the same(similar).
It doesn't see the
light(so to speak) but as soon as I move it notices me.
I had a pair of Tawnys in a Jacaranda at the rear of my yard too for a while, and always during the daytime. No nest that I could see.
But I was in the process of building a shed right near the tree, and once the excavation work started it scared them out, have yet to return
The fruitbat is going to be hard due to it's colour!