I saw one bird on an exposed part of the island, outside of the reeds growing around it. The bird looked like it was gathering nest building material as it used its beak to tug at some dead reeds on the bank. Eventually, the bird flew off with some vegetation. It, or another bird, would climb some way up the reeds before disappearing back into a clump that was just too far in among the reeds for me to see the birds. However, a bird suddenly flew up onto a larger stalked plant before descending down its trunk. For the next 20 seconds all I could was this stouter plant waving backwards and forwards very roughly among the thinner surrounding reeds. Eventually, the bird flew back up with a far more moderately sized reed in its beak before once more descending into that hidden clump of foliage where I assume that it was building a nest. Again and again I saw these birds climb the reeds, sometimes calling, other times flying rapidly between individual reeds. There may have been up to three birds in that clump of reeds.