I am reluctant to ask for ID assistance without a photo, but when I came back with my camera, of course the bird had flown.
In the bird bath mostly frequented by sparrows, just half an hour ago. The bird had the size and shape of a thornbill, it was plain dark brown without any distinguishing markings. Even the abdomen was pretty much the same colour as the rest of the feathers. Light was dappled shade, but I did have the sun behind me, so it was not the case of looking at a silhouette. What made me look in that direction in the first place was a brief Zitting sound similar to white-browed scrub wrens, but most of the time it was silent.
I can’t find a thornbill that fits that description, so what might it be?
The location of my property is a small block near Erindale, neighbouring gardens are sadly lacking in native vegetation.