A pair seemed to use the hollow as their nest. One of them went into the hollow. While they made a short trip to the river for a few minutes, a pair of Galahs came to the tree. The female Galah started to chew the entrance of the hollow then the Grey Teal pair flew back. The male Galah chased the Teal pair away. It seemed the competition over the hollow was going on. The hollow was very high up - the photo no.5 shows it in the circle.