Repeat observation. Pair showed up after 10 min. Male inspected hollow. This hollow is very high (guessing about 15 meters). They were very aware of me being there, I hope the monitoring will not dissuade them from using this hollow.
Thanks Martijn. Once you have observed gang gang you do not need to spend full 20 min at site and you can stand back from tree. Several of our known nest trees are very close to walking tracks and were frequently observed last year so I don't think your occasional short visit should be a problem