Watched the hollow from 11:25 - 12:20 am not sure what is going on but suspect that a pair is either preparing to nest again or preparing a hollow for next season.
On arrival the female was about 1.5m along a branch from the hollow and the male was in the hollow. They swapped being in and out of the hollow on 4 occasions but the male spent longer in the hollow and snapped at the female when she came out. While the male was in the hollow I dd see a shower of bark debris come out of the hollow as if he was using his feet to kick out debris. On two occasions I also saw the female poke her head into the hollow and emerge with bits of wood in her beak which I assume were passed up be the male. No juvenile birds were in sight and no chick poked their head out of the hollow. At 12.10 the female flew off to the north calling. the Male left in the same direction 5 minutes later.