Many will have read by now the discovery by researchers, of Sugar Glider predation on Orange-Bellied parrot sitting females, nestlings and eggs.
On my property, there are the usual non-native predators of foxes and cats. In the first year here, I recorded footage of two cats raiding a Scrub Wren nest right outside my back door, taking and killing the single chick that was just about to fledge. This happened in my first Summer on my bush property. Foxes are semi-frequently recorded on my wildlife cameras, these I actively control however. There were originally 6 foxes visiting different areas of my property every night of the year. New foxes do move in – there was a 12-18 month quiet spell, but I keep an eye out with the wildlife cameras and remove them also.
This fox is no more!
Common native predators of nest box occupants, eggs and chicks include Brushtail Possums, Sugar Gliders, Ravens and Currawongs. Depending on the species and abundance of predators in the neighbourhood, your selection of location and other methods of protecting a nest box from being raided by a predator will drastically improve occupancy rates and nesting success of any target species.
I recorded footage of a Brushtail possum dragging a female sitting Wood Duck off her nest at night, attempting to kill her before she escaped into the darkness with her life. The nest was abandoned, 18 eggs laid and 14 days of sitting for nothing.
I have also observed on my property that Ravens enjoy snacking on Wood Duck eggs, Brushtail Possums will happily raid any nestbox they can fit into, and the resident Sugar Gliders also enjoy Crimson and Eastern Rosella eggs.
Check out the below link, and also the Predators & Competitors link above in the top menu for more species specific information on keeping your nest box target species safe.