Many of Australias wildlife species live and/or nest in native tree hollows. Different species have different requirements for example, type and orientation of opening, vertical or horizontal chamber/hollow.
The size of the hollow required usually depends on the size of the animal. However, as the size of the hollow increases so does the time it takes to be created in the tree.
Large hollows suitable for possums, kookaburras and cockatoos can take up to 100 years to develop and often require the assistance of termites to get started. Unfortunately, in many of our urban areas old eucalyptus trees and especially those with termites are usually the first to be cut down for safety concerns.
Artificial Nesting Hollows
Nest boxes are a type of “artificial hollow” and can be used to provide a form of substitute habitat in areas that don’t contain or cannot support large hollow bearing trees. Nest boxes can be erected in existing smaller trees or can be attached to a purpose built pole located in or adjacent to existing vegetation/landscaping.
Erecting a nest box (or 2) in your backyard can provide valuable nesting habitat and housing for many birds, bats, gliders and possums. It may also help prevent possums using your roof as one very “big hollow”.
In South – East Queensland we have 87 species of birds, 35 species of reptiles and 55 species of mammals that will utilise tree cavities for shelter and/or nesting. (Source: Hollow Log Homes)
Tree hollows required by larger species such as possums, cockatoos, kookaburras and even some duck species, can take anywhere between 100 to 200 years to form. Generally over this long period a mature tree will develop multiple hollows of various sizes as a result of fire, termites and limb drop. These old growth trees are often referred to as apartment blocks for wildlife. In nature individual tree hollows may be used by several different fauna species over time and some individual fauna species will also utilise several different tree hollows throughout their range. Unfortunately in urban environments these old growth trees are most often considered a danger to people and are usually the first to be cut down. Their habitat value and ongoing contribution to natural ecological cycles is irreplaceable and lost forever.
While it is not possible to replace all the natural hollows lost to development and urbanization, the installation of artificial nesting boxes can be used as a substitute in urban areas and also to increase nesting opportunities within natural bushland areas.
Tips on choosing the right Nest box and placement
- Choose the species you want to attract into your garden and ensure your nest box is suitable for that species in terms of size, shape and entrance.
- Ensure you have an appropriate site to locate and hang your nest box and that your backyard habitat (and surrounding habitat/area) is suitable to support your chosen species. (For example if you have a small backyard with no large trees it is not recommended to choose a large box for cockatoos).
- The box should have drainage holes in the bottom and a secure lid or roof to keep water out.
- Attach the box securely to an existing tree (or purposely erected pole 1)
- Orientate your nest box on the side of the tree that is not exposed to prevailing wet-weather, cold winds and direct sun. Preferably the box should be located in shade or semi-shade or within foliage.
- Nest boxes should be placed at a minimum height of at least 3m – 4m up the tree trunk or as high as possible and be out of reach from cats or other pets
- Depending on the time of year that you put your nest box up, it can often take some time for a new resident to move in, so you may need to be patient.
Alternatively, a purposely erected pole could be used if no suitable trees are available. Never use timber poles treated with chemicals and ensure cats or other predators cannot climb the pole and gain access to the box.
If hanging a nesting box for birds that don’t need to climb the pole to get to the box, consider using a steel pole or placing a steel barrier plate around the pole to prevent predators from climbing (ensure it if fixed high enough that cats cannot jump above it). When locating the pole, ensure that cats and other predators cannot reach the box or jump from any adjacent fixtures such as trees, fences, roofs etc.
Nest boxes aren’t all the sameThere is no single nest box design for all fauna species. Many of our wildlife species have very specific requirements when selecting natural hollows. As such, nest boxes need to be designed and constructed to incorporate essential characteristics that mimic their needs in natural nesting hollows.
For example, most cockatoos, rosellas, possums and gliders need a hollow or nest box which is vertical, while other parrots often prefer theirs nesting hollow to be sloping.
Kingfishers, including kookaburras, prefer hollows or nest boxes that are horizontal.
The size of the entrance hole and cavity in the hollow or nest box also determines what fauna species will use it. (ie – who can fit in the hole).
Links and Other Resources
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Useful Tips and Facts
- Create urban wildlife corridors and stepping stones to larger local bushland or parkland areas.
- In nature there is no such thing as waste everything is linked and contributes to the cycle. As a plant reaches the end of its life cycle it is not discarded by nature, instead it provides habitat for animals and food for micro-organisms as it lies on the ground, the waste from the micro-organisms, bacteria and fungi feeding on it replace nutrients and organic material to the soil for new plants to grow.
- Plant local native species
- The best way to attract native wildlife to your backyard is to provide a variety of healthy natural foods in the form of seeds, leaves, flowers, nectar, pollen, fruits and nuts throughout the year.
- The use of pesticides and herbicides can damage your soils and kill non target species. The poisoning of insects with chemicals can also cause larger species relying on those insects as a food source to become sick or even die from eating poisoned insects.
- To create habitat for smaller native birds you can grow shrubs close together to create dense corners or pockets in your garden which will provide protection and refuge from larger aggressive birds such as noisy miners
- Wattles (Acacias). While most wattles only live between 6 - 10 years, they are an important pioneer species which colonise disturbed areas, where other plants find it hard to grow. They improve soil conditions enough to allow other species to germinate and thrive by fixing nitrogen into the soil through their roots and adding high levels of organic leaf litter.