Hollows as Homes
In urban and agricultural areas large, hollow-bearing trees are in decline, but many species of animal rely on tree hollows. Nationally, hollow-using species include at least 83 mammals, 114 birds, 79 reptiles, 27 frogs and many insects (e.g. bees) and spiders. Of these, at least 64 (22%) species are listed as threatened with extinction. This is why the ‘loss of hollow-bearing trees’ has been listed as a key threatening process nationally. Hollows as Homes is a citizen science program asking you to report hollows in your local area, and the wildlife using the hollows – but more on that later.
Farms and agricultural areas are often characterised by large, old, isolated trees, or small clusters of trees. These clusters often act as ‘stepping stones’ and can be vital in linking up other small patches of trees on adjacent farms, allowing wildlife to more easily move throughout the landscape. Even an isolated tree with a hollow can provide valuable habitat and provide a nest or roost for an animal that would otherwise not be able to live on that farm. A good example of an animal that depends on clusters of trees on farms is the Superb Parrot, listed as vulnerable to extinction, which uses paddock trees for nesting, feeding, perching and protection. Retaining existing hollow-bearing paddock trees, along with ensuring that younger paddock trees are maintained so that they can form hollows, and gaining a greater understanding of how wildlife use paddock trees is vital to maintaining wildlife in our agricultural areas.
It’s not just on our farms that hollow-bearing trees play an important role, but within the bush and urban regions as well. Large old trees, those most likely to contain hollows, are rare in urban areas. If you are lucky your local-park or street may contain a grandparent of the former bush; a large old tree. If you are even luckier, this tree will contain hollows – this isn’t guaranteed. In general, our urban areas contain young trees, however it is likely that many of the species planted will never form hollows, or be allowed to form hollows for reasons of public safety (in case the tree fails). Urban bushland typically contains only half the number of hollows that are present in bushland outside metropolitan areas, and there are fewer hollows in urban parks and streets. Importantly, not all hollows are the same, and some wildlife prefer particular types of hollows (for example a deep hollow, a hollow with a small entrance or a ‘pipe’ style hollow). When we lose the hollow-bearing trees, we also reduce the number of different types of hollows, which can result in competition between wildlife, with some species losing out to more dominant species, for example the rainbow lorikeet taking a hollow from the eastern rosella. It has been shown that there are more aggressive interactions at hollows in urban areas than there are in natural bushland.
Hollows as Homes aims to increase our knowledge and understanding about tree hollows; the distribution of tree hollows, the types of hollows available and how wildlife use tree hollows, including nest boxes and cut-in hollows. In areas lacking natural tree hollows supplementary hollows, in the form of nest boxes or cut-in hollows, are often provided. However, the effectiveness of these alternatives is still not entirely understood. To help us understand more about how wildlife use tree hollows, nest boxes and cut-in hollows, we are asking people join-in the Hollows as Homes program www.hollowsashomes.com. Choose a tree in the garden, street, park, bush or paddock that has a hollow or a nest box and report it through the website (this works as a web-app on your phone). You can provide details about the tree and hollow, such as tree height and the direction the hollow is facing. Ideally the hollow is in a location that you periodically encounter, e.g. while walking the dog or sitting in your garden, this provides regular opportunities for you to observe wildlife using the hollow. If you see any animals or insects are using the hollow you can add these observations to your original report of the hollow through the website.
In addition, people can participate as a group, designating an area that they regularly visit and collectively assessing the trees for hollows and adding wildlife observations. The group option is ideal for bushcare sites, landcare programs, parks, schools, gold clubs, community gardens, etc. An unlimited number of people can participate in a group, and importantly anyone who is part of the group is able to both view and add wildlife sightings to any of the reported tree hollows or nest boxes within the group boundary.
The information reported through Hollows as Homes will be accessible to the public, and importantly to land managers. Ideally, this information will inform conservation planning to conserve habitat trees, and the provision of supplementary habitat.
For information on how you can be a part of this program, visit www.hollowsashomes.com or facebook.com/hollowashomes. Alternatively, you can email Dr Adrian Davis at firstname.lastname@example.org for more information.
Hollows as Homes is a collaborative program between the Royal Botanic Garden Sydney, University of Sydney, and Australian Museum. It is supported by funding from the Australian Government.