What it this bird?

Several months ago, March 13 my camera said, I saw this little bird on the fence. At first I thought it was a sparrow but it looked different somehow with the naked eye, but it was about the same size as a sparrow. I only saw it from the angle in the photos, which are heavily cropped from the originals. I live in Tenterfield, NSW. This bird only hung around for a day or two perhaps and hasn't been seen since. Any ideas of what it could be?

Please note, the yellow-green colour on it's underside is a light reflection from the plants below the bird.