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  • Writer's pictureKatrina

Holy Hollows

Hollows are critical for many native species for breeding and shelter. They are possibly one of the most under-considered features of an ecosystem when any kind of development is planned that will result in removal of existing habitat.

Storm Damage
Storm Damage

Eucalypts in Australia are a major source of hollows and species that rely on them include gliders, possums, ducks, kookaburras, owls, tree martins, parrots, kestrels, falcons, kingfishers, echidnas and bats.

You often won’t even notice the hollow walking past a mature tree because being partly hidden is a safety feature.

There are 2 main types of hollows – high up within living trees, and on the ground within dead trees. Dead trees, whether left semi-upright within dense bush, or lying on the ground provide invaluable resources to an ecosystem. People often think they look unsightly, but they are totally teeming with life, even if you don’t notice it walking past one. The uses for dead wood in an ecosystem are basically endless.

Hollows in living trees are formed as a later result of an injury of some kind to the tree. This injury could be a limb that is torn off during a storm, or attack to the bark by insects or their predators.

Limb Damage
Large tree limb torn off during a storm

If we stop, step back a little, and look at the big picture, we just may find that things we think are negative are actually a part of the great cycle of life that Mother Nature is orchestrating. Death and life go hand in hand, around and around, from the microscopic level up to the largest of living beings.

However, creation of hollows in living trees takes time – and I mean it takes a long time. We can expect a minimum of 80 years before a new sapling has developed into a mature tree containing hollows that our wildlife can breed in. It can take more than 200 years for hollows of sufficient size for our larger species to develop. OK just stop, step back a little and think about what that means. We just don’t do well thinking in these kinds of time frames do we? If I decided that this old tree doesn’t suit me, and I remove it, where are these animals going to live and breed while they wait 200 years for the little seedling I planted to grow?

Hollow Forming
The sap here is likely being fed on by gliders and parrots and is a typical example of a slowly forming hollow.

Each time a storm or fire or flock of large parrots comes through, damage happens. Branches break, are blown down or breached in some way. Fungi may set in and attack the wound further. Sap may leak out causing more damage as it attracts gliders or more parrots to feed and scrape the area away.

The chances are that this wound will develop into a hollow. It may take another 50 years, but this is town planning at its best. Providing for future generations by setting up situations where growing trees will have hollows for all kinds of species.

Yellow-tailed cockatoo and result of one removing borer larvae from a young tree, setting up the start of hollow formation.

If you have any wildlife around you, even in a backyard setting, you can consider creating some hollows by putting in nesting boxes. Do a little research to find out what species live in your surrounding area, and what is most at risk. There are a range of types, sizes and entrances to boxes depending on the species you are targeting, so a little research will likely give you some great results while the next 100 years of growing forms natural hollows.

Nesting Box
Parrot nesting box on mature tree that will one day have hollows higher up where birds and gliders feed on sap.



This article has been kindly supplied by Katrina Jeffery of Koala Gardens. Follow Katrina on Facebook here, and for the fascinating history of Koala Gardens please see the following webpage:


Did you know Katrina also has a children's book? "The Adventures of Mist: Finding Koala Gardens" is available on Kindle. Find it on Amazon here.


Adventures of Mist Book 1 has been published. You can order now! Age 5-10 years (and adults love it too!)

1 Comment

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Rebecca D. Thomas
Rebecca D. Thomas
Aug 28, 2018

This is a great post, and very informative! I did not know about the importance of hollows! I've learned a lot by reading this post!

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