On arrival the adult male was looking into hollow. He spent about 10 minutes at the hollow moving around it, looking into it, and calling with wings outstretched while looking into it. Sitting in the same tree were a female, and two immature males.
Here are some links to videos of the male at the hollow:
https://youtu.be/H5FTbOI90Vg,
https://youtu.be/UWdrtHZ0dKI,
https://youtu.be/V8WH6K0HUeg