I came across a different Sulphur-crested Cockatoo in a different hollow just outside the reserve. The bird was on the edge of the hollow but occasionally biting at the wood. The hollow appeared to have a reasonably wide opening but was also exposed vertically, perhaps making it too easy for rain to enter. The bird climbed around in the hollow but did not enter it fully so I was unable to see if the hollow could accommodate a breeding bird. The bird appeared nervous with my presence, it sometimes seemed like it was ready to fly away, so I did not stay long.