There were several groups of them active across that region in a half-hour period: four flying between a few thickets of trees above the path, and two groups of at least four flying in periodic loops around the valley, pausing intermittently to land on a couple of prominent trees. I was trying to be conservative with my figures, and observed far higher numbers clustered together at Namadgi (Yankee Hat) a few weeks ago, so I didn't think it was unusual - happy to be corrected though (I thought those were flame robins at the time, and only realised they were scarlet when logging these)!