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Some Australian birds are pushing out other species, and even damaging trees. Noisy and bell miners are two of Australia’s most aggressive bird species. Found throughout eastern Australia, in recent years their numbers have increased at the expense of our smaller birds.
Both species are spreading to new areas, largely due to human destruction of habitat. Noisy miners are able to invade areas where habitat has been modified, particularly gardens.
Bell miners, meanwhile, can invade areas that have invasions of weeds in the understorey such as blackberry and lantana that they use for nesting.
The good news is we can help stop the spread of these birds, by putting native plants in our gardens.
Both species of these miners (genus Manorina) have been found to reduce bird diversity through their aggressive behaviour, and have been associated with eucalypt dieback.
Human disturbance has been linked to increasing numbers of noisy miners. One study in the box-ironbark forests of southeast Australia, found that noisy miners an move into areas of smaller fragments and unhealthy trees.
They then chase away other birds, reducing the number of species and potentially having knock-on effects on ecosystems. The problem is so serious that noisy miners are listed as a national threatening process.
More research is needed to find out why bell miners are becoming more common. But our research has found that bell miners show similar behaviour to noisy miners. They have a distinctive call that travels for tens of metres through the forest.
Bell miners cause Bell Miner Associated Dieback in trees. It is thought that their feeding and breeding behaviours lead to the death of eucalypts on the east coast of Australia. They also take over habitat that would be used by other birds.
Where miners are normally found in lower numbers, disturbances by people can tip the balance in their favour. This includes increasing noise levels, removing corridors of connecting native vegetation, creating gardens with exotic plants, building cities, houses, parks, logging and introducing invasive species that create thick understories.
These disturbances increase the habitat available for these two species, allowing them to increase in number and drive out the smaller birds that compete for their food sources.
Noisy miners particularly favour open areas that don’t have thickets of shrubs of smaller trees underneath the canopy. Conversely, bell miners prefer thick understoreys, particularly those create by introduced weeds such as lantana.
So if we are causing these birds to increase in number, how can we reduce their numbers and re-create the original habitat where all species could co-exist?
You need to create a multi-layered habitat of ground covers, small and medium shrubs, and trees that provide food and shelter locations all year for a variety of species.
These plant species need to have diverse structures, and should be close together to form dense, protective thickets, including climbers within medium-to-tall shrubs and trees, nectar-bearing and seed-bearing plants. Mulch can also encourage insect life for insectivorous birds.
Plants should also be local species that grow naturally in the area and are suited to the climate. Native birds that live in the area will then visit your garden as another food source in their territory.
Reducing weeds in your garden and neighbouring bushland (many weeds are derived from garden plants) can help native species. General natives can also be planted if you can’t find local natives in your local nursery.
Even in gardens where noisy miners dominate, smaller birds can survive in a dense understorey.
Meanwhile, a thin midstorey with fewer leaves may help to reduce bell miner abundance, as suggested by our recent study near Kyogle, New South Wales.
You should also consider the timing of flower and fruit production, to ensure that there is always food available for birds. You should also remove fruiting plants such as cotoneaster and blackberry that attract predators such as currawongs, to help reduce predation on smaller bird species.
Using chemical-free weed and pest control and mulching garden waste can also increase the food available for birds.
Lawns can also be replaced with native grasses that produce seed to attract finches and other seed-eaters such as crimson rosellas. Birds also need fresh water, which you can provide with a pond or bird bath. This should be placed within vegetation to ensure birds feel safe from predators.
Local biodiversity can be maintained by native gardens, ensuring long-term ecological sustainability. Small birds and other wildlife benefit from planting native species.
Many species are negatively affected by the current structure of gardens such as lawns, few scattered trees and the placement of concrete and houses without any access to nesting habitat.