Brushtail Possums enjoy snacking on eggs, nestlings and even adult birds if they can catch them. Our property has an unusually high population density of Brushtail Possums, because a Wildcare neighbour has soft-released numerous possums over the years and they have not ventured far. I estimated that here are probably about 20 Brushtail Possums on our 5 acre property. Our nesting birds don’t stand a chance! So I must possum-protect all but the for-possum nest boxes to prevent them from being raided.

One of our resident Brushtail Possums dragging a nesting Wood Duck from her nest box. She just managed to escape with her life, and did not return to sit on her nest of 18 eggs for obvious reasons!

Through a discovery process of trialing different possum guard and nest box placement methods, monitoring by wildlife camera, plus frequently checking inside the nest boxes myself, I have discovered just how agile Brushtail Possums are. Unless a tree is completely solitary, with no part of the nest box tree canopy close to the canopy of a nearby tree, a Brushtail Possum can easily climb down a tree to access a nest box after crossing from the canopy of a nearby tree. 

My typical method of installing Brushtail Possum guards. One below, and one above the nest box on a nice, straight tree with no nearby (4m+) tall shrubs or trees – or trimmed to below the possum guard height.
An easy tree to possum-protect, with no trees within several meters. There is a possum guard at about waist height, then one just above the nest box. A successful Eastern Rosella nest box this year.
A black cockatoo nest box design, successfully used by wood ducks this spring (2019).

This means that possum guards both above and below nest boxes are essential. This also means that even if there is a very small dangling small twiggy branch next to a nest box on a tree with possum guards, a possum can simply use this twiggy branch to access the nest box directly.

Possum guard fail! While not a predator, if this Ringtail Possum mum and bub can cross using these flimsy thin branches, so could a Brushtail Possum. This nest box & possum guard installation was to test polycarbonate plastic tree trunk guards above and below the nest box, and also polycarbonate plastic panels installed on all sides of the nest box except the front to prevent a possum from climbing onto the nest box. Hmmm, nope. I was hoping to find a method to possum-protect nest boxes installed within lots of vegetative cover to hide the nest and feeding parents from daytime predators. Still working on it…

Guards as close to the nest box as possible reduces the risk of a possum accessing the tree via a close branch that you may not have noticed (it happens!), and reduces the area that a glider can land on from a nearby tree. My successful nest boxes are on straight, solitary trees, with no (or trimmed to 1.5-2m away) nearby branches, no matter how small and insignificant they look! 

A successful nest box for crimson rosellas last year.

This is my next problem to work on, as small birds vulnerable to predation need to nest in places obscured by leaves and branches. No doubt the first flight of any nestlings will be much safer, with close branches to land on and recover, than having to launch to a far-away tree. Mum and dad are at risk too, when feeding hungry youngsters. Mmm the perfect Currawong snack…a fledgling’s first flight. 

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Predators & Competitors

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