A nest of yellow-rumped thornbill in a Bursaria shrub; the photo shows the real (lower) entrance of the well-camouflaged nest. I spotted a second nest in another Bursaria approximately 2 meters away however the structure of the nest was simple and I'm not sure about the bird species.
Hi Waltraud, if you're confident you can confirm yourself (I believe you are a Mt Majura Moderator), its a bit difficult to be confident from your image.