Common brushtail possum Trichosurus vulpecula evicts juvenile southern boobooninox novaeseelandiae from its nest-hollow

We describe conflict between a breeding pair of Southern Boobooks Ninox novaeseelandiae and several Common Brushtail Possums Trichosurus vulpecula that culminated in a possum entering the Boobook's nest-hollow and eating most of a clutch of eggs. However, one egg hatched, although a possum subsequently caused the young Boobook to fledge prematurely. After the juvenile could fly well, the Boobook family vacated the hollow-rich nesting patch for a foraging area that lacked hollows, where the juvenile reached independence. In the following year, the Boobooks nested again in the same tree but lost two clutches (in different hollows) to possums, which then occupied one of the hollows, before finally fledging two young from a third hollow (in a different tree) ~2 months later than normal. This hollow had been used earlier in the season by Sulphur-crested Cockatoos Cacatua galerita, which harassed the incubating Boobook and tried to enter the hollow. Competition for increasingly scarce hollows, by some species which are already abundant or are becoming more so, may be a factor in the recent decline of Boobooks.