Birds Behaving Badly - Australian White Ibis
The natural habitats of the Australian White Ibis, Threskiornis molucca, are terrestrial wetlands, grasslands and sheltered estuarine habitats, where they feed on frogs, crayfish, fish, crickets and beetles. However some populations have learnt to exploit artificial foods in urban environments and are becoming pests.
Why are ibises pests?
There are four main ways in which Australian White Ibises are considered to be pests:
- When they forage in flocks in the vicinity of air fields, ibises pose a theat to aeroplanes, as their large size means that they are able to break windshields, or damage engines.
- Ibises roost communally and a moderate-sized colony produces a lot of droppings. If they roost in a public area of a city, such as Darling Harbour in Sydney, their droppings can make the area unusable, and might be a problem for human health (though this has not been demonstrated).
- Ibises that become accustomed to people sometimes feed in garbage bins and steal food from picnic areas. While they are quite harmless, some people find their large size, and particularly their beak, intimidating.
- Ibis droppings can modify the environment so that it can no longer sustain particular plants. This means they can be a problem in botanical gardens and some reserves. For example, in Fairfield Local Government Area, Sydney, Australian White Ibises may be destroying the roosting habitat for a threatened population of the Grey-headed Flying Fox (Pteropus poliocephalus ).
How are they controlled?
The National Parks and Wildlife Service has issued licenses for the control of Australian White Ibis populations in special circumstances. Although population control (through shooting or egg-destruction) has sometimes been necessary, a preferable solution is to avoid providing food or waste that they can exploit.
What about their natural habitat?
Unfortunately, although Australian White Ibises are becoming more common in some areas, their abundance is decreasing in their natural range. Diversion of water from inland rivers for irrigation of agricultural products has reduced the ibises' ability to breed in terrestrial wetlands.
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