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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 – http://ab.co/2uDf9fl

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.

Showing two of the new habitat trees - one on the left and the other in the foreground with the sign on the trunk.

Showing two of the new habitat trees – one on the left and the other in the foreground with the sign on the trunk.

Last October the Inner West Council posted that they created three new habitat trees in Mackey Park Marrickville South.   We walked the whole park, but unfortunately were only able to find two of the trees.  The trees we found were between the shared path & the wetland area.

Habitat trees are trees that have caused a safety problem by dropping branches. Rather than removing the tree, the tree is killed by ringbarking.  Then the branches are cut open & a cavity created with a chainsaw to create nest boxes & other kinds of hollows.

A large amount of Australian wildlife will not breed if they do not have access to a hollow, so retaining the structure of mature trees is vitally important.  See – http://bit.ly/1ASqhzz

Council said they created five nesting boxes in these trees.  Three for Red-rumped parrots, one for Gould’s wattled bats (microbats) & one for a Brushtail possum.

They also plan to mulch & landscape with local native plants under & around the trees in the near future.  Good one Council.

Showing one of the nesting hollows.

Showing one of the nesting hollows.

The dead habitat trees are visible from some vantage points

The dead habitat trees are visible from some vantage points

‘Habitat trees’ are trees that have been killed because they are considered dangerous due to dropping limbs or other issues, but left on site.  Their canopy & their branches are removed.  The trees are ringbarked & artificial hollows are carved into the remaining wood.  Sometimes, nesting boxes are also attached.

The idea is that even though dead, the trees continue to provide habitat for hollow-dependent wildlife.  About 350 Australian animals use hollows for either roosting or nesting.  It takes around 100-150 years for a tree to even start developing hollows, so our wildlife is at a distinct disadvantage with tree hollows being very scarce across Australia.

I was really pleased to see the changes around the ‘habitat trees’ in Sydney Park.  I last wrote about these trees here – http://bit.ly/2fQ9DkG

The area around both trees has been extensively planted making what I consider viable habitat for a range of species, especially small birds. Instead of two highly visible standing dead trees, the City of Sydney Council has surrounded these trees with densely planted living trees, shrubs & understory plants. To me it looks like the bush.

I am not good at estimating distances, but my guess is that it is at least 25-metres of thick bush around the two habitat trees.  Already a number of living trees are the same height as the two dead trees.  This provides supreme cover & safety for any wildlife who are using the man-made hollows.

I think what has been created here is perfect.  Real habitat has been provided for wildlife & we are not left with what could be considered an eye-sore of looking at two heavily pruned dead trees.  The trees have blended into the new landscape and are not the only thing ones eyes focus on.

You can sit in comfort at a number of places near this area & watch & listen to the birds making it great for bird photography too.

They almost disappear from other angles.  I love that City of Sydney Council plants densely in some areas.

The dead trees almost disappear from other angles. I love that City of Sydney Council plants densely in some areas.

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 – http://bit.ly/1U6x70v

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.

First sight of the habitat trees from across the lower pond.

First sight of the habitat trees from across the lower pond.

A closer view

A closer view. Both are still very tall trees.

City of Sydney Council has recently created two ‘habitat trees’ in Sydney Park. Both trees are Eucalypts & are located close to the lower pond.   They are surrounded by other tall trees & so would make attractive homes for wildlife.

A significant difference from the ‘habitat tree’ created by Marrickville Council in McNeilly Park is that the branches have not been ring-barked – at least it had not been done when I saw these trees.  It appears that Sydney Council has created more holes in each tree than the one in McNeilly Park.

Showing the damage on one of the trees.

Showing the damage on one of the trees.

Like Marrickville Council, the City of Sydney Council is also using these trees as a demonstration for professionals on to how to create nesting hollows for birds & animals.

I really like this movement to retain trees that would have been removed previously.   The idea is to mimic dead trees found in the bush.

The more I read about dead trees the more I realize how important these old dead trees are to the ecology of the environment.   Standing dead trees in the bush are called snags & stag trees.

Only old trees have hollows & these trees often need to be 100-150 years old before they start creating hollows.  Eucalypts start creating hollows after dropping branches & we know that once branch-dropping starts, the tree is removed for the safety of the human population.

“Australia-wide, 15% of all land birds use hollows. These 114 species include parrots, owls cockatoos & lorikeets, ducks, treecreepers, owls, owlet-nightjar, kingfishers, pardolotes, martins & woodswallows.”  ~ Sourced from Wildlife Notes, Department of Conservation & Management April 2005.

One of the least known characteristics of Australian animals is their high utilisation of tree hollows. For example, the proportion of Australian animals that use tree hollows is three times greater than in North America & twice as great as in South Africa.

About 350 Australian animals use hollows for either roosting or nesting. This includes:


  • half of our small bats,
  • nearly 90% of our parrots,
  • all of our gliders,
  • all but one of our owls
  • all of our tree-creepers.

Nearly 20% of our birds use hollows in some way. For 60% of these, hollows are essential.” http://www.ozbox.net.au/anim&holl.htm

Of the 22 species of bats that have been recorded to utilise tree hollows in NSW, 10 of these are listed as threatened. (Gibbons & Lindenmayer 1997).

Repurposing trees that would have been removed so that they become useful for wildlife is a great idea. Tree hollows in urban environments are very rare.  I look at trees all the time, but only know of three trees on public land in Marrickville LGA that have natural hollows. I applaud this move to help wildlife & improve on biodiversity by both Councils.   It will be interesting to see what wildlife do take up residence in these hollows.

Sign on tree

Educational sign on tree

The back of the nesting hollows.  To show the front would have meant facing the sun,

The back of the nesting hollows. To show the front would have meant photographing into the sun.

Another view.  It's hard to see the hollows, but the more I looked, the more I spotted.  They are on the tips of branches as well as multiple hollows along branches.

Another view. It’s hard to see the hollows, but the more I looked, the more I spotted. They are on the tips of branches as well as multiple hollows along branches.

A hollow has been made at he end of many of the branches.

A hollow has been made at he end of many of the branches.  It’s hard to see, but it is there.

 

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