Eucalypt tree hollows
Eucalypts support a great diversity of life in Australia, providing food, shelter and habitat. They are also an important source of shelter for animals in the form of hollows. It can take quite a long time for hollows suitable for shelter and breeding to form in eucalypts. Fire and practices such as cutting down dead trees in a stand for firewood has had the effect of reducing the availability of tree hollow habitat. And this has a flow-on effect for the animal life that depends on these eucalypt hollows to shelter and raise the next generation.
Diversity of animal life
Animals such as brush tailed possums use hollows in trees.
And so do bats, insects, mammals, amphibians, birds, reptiles and invertebrates.
The presence of eucalypt hollows in a forest is an indicator of the ability of that forest to support a diversity of animal life. One of the aspects that affects which animals can be supported is the sizing of the hollows. For cockatoos, for example, the hollow needs to be quite large. Hollows of these sizes can take up to 150 years to form, depending on the eucalypt species. In the Edward Hunter Heritage Bush Reserve, most hollows that can be seen from the ground seem to be on the smaller side.
The crimson rosella (platycercus elegans) uses eucalypt hollows for their clutches of eggs. An adult can be seen here in the Reserve shifting in and out of the nesting hollow.
The breeding season is from September to January and the female incubates the eggs (usually five). Both male and female birds care for the young, looking after the chicks for a further month once they leave the nest. Young rosellas gradually attain their red adult plumage over 18 months.
Both native bees and the exotic honeybee use tree hollows, too. These two examples from the Reserve were taken in April. It’s a little hard, though, to tell what kind of bees, pictured here, are using these particular hollows – whether native or exotic.
In situations where tree hollows are in limited supply, competition from exotic bees can put a great deal of pressure on native animals.
Animals can be selective about their choice of hollow. Whether it is a useful hollow or not can depend on depth, entrance size, location in the tree and shape. It can also depend on which part of the landscape it is in and how close predators or the same species might be.
Whilst it hasn’t been possible to always see and photograph the animals that use hollows in the Reserve – especially if they are nocturnal or simply not arround when the viewer is – the rubbing marks around these hollows below show they may be good ones.
This one below shows nesting materials, possibly of the common ringtail possum, which uses ferns in its nesting materials.
In this case below, the only way to know if it is in use would be to see inside…
Sources and further information
Birds in Backyards (2013) Crimson rosella Basic information. http://www.birdsinbackyards.net/species/Platycercus-elegans
Gibbons, P. & Lindenmayer, D. (2002) Tree Hollows and Wildlife Conservation in Australia. CSIRO Publishing: Collingwood.
Goldingay, R. (2012) Trees and non-flying mammals: a hollow understanding. ECOS Science for Sustainability. http://www.ecosmagazine.com/paper/EC12338.htm
Koch, A. Forest Practices Authority (2009) Tree hollows in Tasmania: A guide www.crcforestry.com.au/downloads/hollows-booklet-241109.pdf
NSW National Parks and Wildlife Service (2002) Threatened Species Information: competition from feral honeybees as a key threatening process – an overview. http://www.environment.nsw.gov.au/resources/pestsweeds/feralHoneybeesFactsheet.pdf
Parks Victoria (n.d.) Park Notes: Crimson Rosella http://parkweb.vic.gov.au/__data/assets/pdf_file/0012/322203/rosella4.pdf