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Nesting box along the Cooks River in Earlwood.

$200,000 was spent trying to protect wildlife impacted by the Southern Hume Highway Duplication project in Southern NSW.  See –

587 nesting boxes were installed to replace the 587 trees with natural hollows that were felled as part of major tree clearing between Holbrook and Coolac to build the highway.  The nesting boxes were to help the Superb parrot, the Brown treecreeper & the squirrel glider deemed threatened or in need of assistance.

NSW Roads and Maritime Services commissioned the nesting boxes, as well as a 4-year follow-up study to see whether the boxes were being used.  The boxes were checked 3,000 times over the four years.

The follow-up study found the project had failed.

“There will be some populations of these species that basically won’t do well now because they won’t have the nesting resources and they won’t have those resources for the next 200 to 300 years.  We need to make sure we don’t make those mistakes again.” ~ Professor David Lindenmayer, Australian National University Canberra.

Trees take between 80-150 years to develop hollows, so changes in tree management is needed if hollow-dependent wildlife are to survive.  We cannot feel confident that nesting boxes can be offered as a substitute for a natural tree hollow.

No hollow means no breeding.  No breeding leads to extinction.

This tree hollow in Putney Park looks like it is straight out of a fairy tale. It is terrific that the tree has been allowed to stay.

This tree hollow in Putney Park looks like it is straight out of a fairy tale.  It is terrific that the tree has been allowed to stay.

We went to an interesting workshop yesterday called, ‘Hollows as Homes’ organised by Marrickville Council before it became Inner West Council.  The workshop was presented by Dr Adrian Davis, who did his PhD on tree hollows.

Tree hollows are in severe decline.  It can take a tree anywhere from 50 to 150 years to develop a hollow suitable for wildlife to use as a home.  It can take up to 200 years for a hollow to form suitable enough for a large bird such as a powerful owl.

Trees are being chopped down before they create hollows & the lack of tree hollows has been classed as a “Key Threatening Process to biodiversity in New South Wales.”

We have no ‘primary excavators’ in Australia.  A woodpecker is a great example of a primary excavator.  They can quickly create quite large holes in trees while searching for food.

In Australia, decay is needed to create a natural hollow in a tree.  Decay comes after the sapwood has been breached.  This happens only after a tree has been damaged by lightning, wind, bushfire or mechanical damage.  Fungus enters & slowly over decades creates the hollow, which then becomes a suitable home for a range of wildlife, including birds, microbats, bees, lizards, spiders, possums, frogs, snakes & gliders.    Six to eight species may be competing for a single tree hollow.  Tree Hollows also provide drinking water for wildlife, which in itself is important.

As we know, public trees that develop decay are chopped down.

Over 300 native invertebrate species in Australia are dependent on tree hollows to breed.   No hollow for a home – no breeding.  A shortage of tree hollows leads to a decline in species numbers & in some cases, resulting in an endangered species.   It is easy to see how vital tree hollows are to the native wildlife of Australia.  A shortage of hollows also results in a predominance of specific species that are string enough to gain ownership of the hollow.  Locally, these are sulphur-crested cockatoos & rainbow lorikeets.

I did learn something interesting about cockatoos.  They may sleep as far away as the Blue Mountains, but fly to Sydney every day.   I did not know they could fly so far.  Makes me think about the cockatoos who live their life in a cage.

Dr Davis said that in the Central Coast region, 54 species use tree hollows & 13 of these are endangered.    

The ‘Hollows as Homes’ program is the first of its kind in Australia & has the intention of collecting data for many decades.

“Nest boxes and cut-in hollows are often used in areas lacking natural tree hollows, however we don’t know a lot about how animals use this substitute habitat in place of natural hollows. Many animals have specific attributes that they like in a hollow, consequently some animals may not use artificial hollows. For this reason it is important to know if nest boxes and cut-in hollows are attracting the desired animals, or, if they are being used at all. The Hollows as Homes project aims to conduct the first landscape scale assessment of tree/nest box/cut-in hollow distribution, type and wildlife use.”

The program is looking for people who are willing to watch a tree hollow for 10-minutes once a fortnight & then log their observations on the website.  This is a perfect opportunity for schools that have nesting boxes to become involved.

The website has clear instructions about how to get involved & what information to provide.  They are not asking for much.  It would be especially easy for those who have a tree hollow or nesting box in their garden.  Sit & have a cup of tea while watching the box for 10-minutes & help in the creation of data that will be immensely helpful for generations.

If you don’t have a tree hollow in your garden, then you can choose one or more trees locally that do & observe those trees.  The researchers do not care where the tree is, though they do not know how many trees with hollows or nesting boxes there are in private gardens, so this information will be very useful.

If you missed the training at Marrickville, the website shows upcoming workshops & all are free to attend.  For more information see –

I was surprised to find a nesting box close to a seat that I sit on at least weekly.    This might be my choice for the program.

I was surprised to find a nesting box close to a seat that I sit on at least weekly.   This might be my choice to observe for the program.



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