Into the hollow: Exploring the value and role of naturally occurring tree hollows

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Into the hollow: Exploring the value and role of naturally occurring tree hollows

This Hollow-ween we’re celebrating the valuable role that tree hollows play as an essential part of native ecosystems. While they can look scary, these fascinating spaces provide refuge and habitat to native insects, birds, bats, reptiles and mammals, making them the original sanctuary for native biodiversity.

Hollows are naturally occurring cavities found in the branches and trunks of trees. They are found in native ecosystems the world over and occur in trees both dead and alive. They provide native animals with a space with a multitude of uses – as habitat, nesting spaces, as a source of refuge during extreme weather events and more.

Into the hollow: Exploring the value and role of naturally occurring tree hollows

Hollows are created by a number of natural processes including fire, chewing and burrowing insects (such as termites) and the effects of naturally occurring bacteria and fungi. It takes around 100 years for a hollow to be formed and they continue to provide important services to visitors long after the tree has died.

Some species use hollows on an ad hoc basis during their lives whereas others are completely dependent on them throughout their entire life. Brushtail possums are one example of a species that is heavily reliant on the hollows found in trees in Eucalyptus and sheoak woodlands. Their nests (also known as dens) are made in hollows and, as a nocturnal species, they use hollows to sleep in during the day. Being off the ground also offers them a valuable source of protection from predators.

Into the hollow: Exploring the value and role of naturally occurring tree hollows
A barn owl keeps watch from the safety of a hollow

Regent parrots rely on hollows in river red gums as a space to create nests in. As part of a 3-year project on nesting and breeding success, ecologists from the Murraylands and Riverland Landscape Board will soon be measuring hollows used by regent parrots in order to develop a better understanding of the dimensions they require. This information will provide valuable insights into the number of available hollows that meet the needs of the vulnerable regent parrot population.

Into the hollow: Exploring the value and role of naturally occurring tree hollows
Regent parrot eggs located in a nest in a hollow at Markaranka earlier this year
Into the hollow: Exploring the value and role of naturally occurring tree hollows
A regent parrot chick found soon after hatching

Because hollows take so long to form, the effects of land clearing on native biodiversity are amplified. While planting new trees is a step in the right direction, new hollows will take almost a century to be formed. If you’re keen to help the species that rely on hollows, there are a number of actions you can take to help:

  • Undertake revegetation work and plant native trees
  • Protect existing trees to give hollows a chance to form
  • Leave dead wood on the ground, especially logs with existing hollows
  • Install nesting boxes
Into the hollow: Exploring the value and role of naturally occurring tree hollows
Hollows provide native animals with a unique view of their local landscape

This project is supported by the Murraylands and Riverland Landscape Board through funding from the landscape levies.

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