There are numerous native animals that are dependent on naturally hollowed out sections of trees.
These cavities can occur within both living and dead trees, with an entrance to the outside environment where the animals can enter and exit from.
Natural hollows range in size from small cracks to large vertical hollowed out cavities similar to a chimney.
These hollows can occur in the trunk or horizontal limbs with the hollows and entrances at any height.
Bush fire, lightning strikes or breaking branches can expose the trees to the elements and the cavities are then largely created by termites, beetle larvae and moth larvae which feed on the internal dead wood of the tree (heartwood).
Fungus can also assist with rotting the timber and fire can further influence the enlargement of the cavities.
These cavities allow the animals to shelter and breed.
Most native trees in Greater Warrandyte are around one hundred years old and are regrowth from the last large scale mining ventures that ended around the beginning of WWI, in 1914.
Some of Warrandyte’s native animals such as gliders, phascogales, possums, parrots, ducks and owls are unable to create their own hollows.
Different animals have different nesting requirements, mainly due to their size.
Nest boxes provide an important supplement to the lack of naturally occurring hollows, in particular the larger ones.
Increasing in popularity is the creation of artificial hollows cut into the trunks of dead trees.
Throughout Melbourne I have seen a growing trend of large dead trees being trimmed of branches and cavities being cut into the upper trunk.
Most of these animals use multiple hollows and regularly change hollows.
This helps keep their hollows clean and free of parasites or disease.
It also helps them avoid predators such as owls which quickly learn which hollows are in use.
Because they rotate homes we need to provide multiple nest boxes to support each individual animal.
I aim to provide two to three nest boxes for each target animal.
Natural tree hollows provide excellent insulation against the cold/heat and last for a very long time.
It is very important to use thick timber or materials that are strong, rot/rust proof and have adequate insulation properties for animal comfort.
I use treated pine that is at least 25mm in thickness as this will begin to provide enough thermal insulation for wildlife.
I also use screws and hinges that are corrosion free and paint the interior and exterior for aesthetics and longevity.
I fasten internal ladders for both marsupials and birds.
They will also provide grip for the young animals that might struggle with climbing.
I also cut external grooves entirely around the entrances for possums to grip on.
I have studied possums exiting the nests at night and they tend to immediately climb upwards so it is important to have grip around the entirety of the entrance.
When installing the nest box I will select a location away from general disturbance and bright lights.
I like to orient the nest box on the side of larger trees and on the south side of the trunks away from the hot afternoon sun.
As most animals will use boxes at about four metres high I usually install the box using a large ladder such as an extension ladder.
Ensure the ladder is tied to the tree for safety and remember that you will want to access your box to inspect it later.
The higher the installation the further away from disturbance the animals will be.
I usually fasten the boxes using plastic coated wire.
As the growing tree trunk expands this may require adjustment over time as it gets tighter.
Spring-wire can assist with allowing the attachments to expand and require fewer adjustments over time.
Generally, you do not need to clean your box.
I will deposit fine mulch in the base for comfort and further insulation.
Most wildlife keep their nests clean.
A few species, such as the phascogale, will soil the inside of their boxes.
That is their normal behaviour.
Cleaning your boxes may stress the animal and cause the animals to temporarily desert the box.
A few small holes or gaps in the base of the box can help drain any water and keep it dry.
It may only take days or weeks before animals such as possums move in whereas others that are seasonal, such as birds, you may have results during the breeding seasons, usually in spring.
Also remember that wildlife move between hollows (and nest boxes) on a regular basis so some of the boxes will be vacant at any given time.
You will often find signs that your box has been used (feathers, scats or nest material including bark or leaves) even though the animal is not at home.
I usually incorporate folding lids that are the easiest way to check inside boxes.
Increasingly popular is the installation of cameras either inside the box or by installing an automated wildlife camera on a nearby tree.
This will monitor what comes in and out of the box.
These pictures are a sample of some of the recent success I have had with providing homes to our local animals in Warrandyte.