Australian wetland birds
The main groups of wetland birds are grebes, pelicans, cormorants, long-legged wading birds (such as the heron) and waterfowl, as well as a large group known as 'waders'. Waders include a variety of birds including godwits, knots, snipes, tattlers and sandpipers.
Australian wetlands provide a range of feeding grounds for these different birds. Snipes feed in long grass at the water's edge, plovers along the muddy shores; herons stalk the shallows, while grebes, ducks and cormorants feed in the open water. Some birds could not survive without wetlands; others may use them only to raise their young or to roost.
Waders range in size from the tiny stint, about 15 centimetres tall, to the curlew, which stands up to 60 centimetres tall. They also come in different shapes and colours and have a variety of bills, some very oddly shaped. The shape of the bill reflects a bird's feeding habits.
To date, 69 species of wader have been recorded in Australia. The vast majority of these migrate. Most fly 11 000 kilometres from the Arctic, via the Asian mainland, to arrive in Australia via our northern shores in September - October. They then return to their Siberian breeding grounds in April - May. An estimated two million migratory waders enter Australia each year.
While in Australia, migratory waders like to keep together. Most of them feed and roost in coastal wetlands, usually roosting at high tide. They may travel some distance to find food on exposed mudflats. Some of those that do not migrate also move around looking for food, especially the plentiful supply that follows rain. This is particularly so in Australia's arid inland.
More information on migratory shorebirds can be found on the ABC web site .
Migratory waders shed their bright feathers for those of a duller shade in the non-breeding season. Often, their more attractive plumage returns before they leave Australia to fly back to their northern breeding grounds.
Australia's three grebe species rely totally on wetlands, which provide them with food (such as small fish and worms), protection (the birds dive to escape danger) and nesting sites (the birds nest on floating vegetation). Grebes have large lobed feet, set well back on their bodies. Although they are very well adapted to life in water, they are clumsy on land.
Four of Australia's cormorant species are found in freshwater and coastal wetlands in all States. (One species, the Black-faced Shag, is found only along the rocky coasts of southern Australia.) Cormorants are medium to large birds (50–85 centimetres tall) with webbed feed, long hooked bills, long necks and either black or black and white plumage. All species feed on fish, insects and crustaceans (shrimps, for example). Usually, they obtain their food by diving underwater.
The darter looks a bit like a cormorant except for its long, snake-like neck and sharply pointed bill. Darters are found in all Australian states except Tasmania, but prefer tropical and sub-tropical regions. The birds swim with only their necks and heads above water. They dive to catch a fish, spearing it with their bill before returning to the surface to swallow it. Darters tend to nest alone, although some small groups are known to live together. Like cormorants, darters nest in trees or on rocky ledges.
The Australian Pelican - one of our most distinctive birds - is found in coastal and freshwater wetlands all over the country. The birds work together to gather food. Groups of them will surround schools of fish, driving them into shallow water where they can be caught more easily. Pelicans nest in groups on sand spits or islands. They make a nest by scraping a shallow hole in the soil.
This group of wetland birds includes a number of species: the heron, the egret, the spoonbill, the ibis, the stork and the bittern. All have long, slender necks; long legs, with long, unwebbed toes; and large bills, shaped to suit the way each bird feeds.
Herons and egrets are found in all types of wetland, although two species are tropical birds. There is also a small family of herons that are active at night; the Rufous Night Heron is the only member of this family found in Australia.
As their name suggests, spoonbills have flat, spoon-shaped bills. They feed by moving their heads from side to side in a sweeping movement.
The ibis has a long, downward-curved bill, which it uses to snap up food such as large insects or to probe in the mud for hidden prey.
Bitterns feed and nest in reed beds or in thick vegetation on the water's edge, and can fly long distances. If disturbed, they tend to become secretive. The bird has a booming call, which is often heard at night.
This group of birds, known as waterfowl, includes 21 species that breed in Australia. (Two are introduced.) Another species, the Garganey, migrates from Eurasia to northern Australia during the summer. Most species of waterfowl are found in the southern part of our continent. However, five are found all over Australia and another six are found mostly in the tropics.
Population numbers vary rapidly according to the food supply which, in turn, depends on the rainfall. In the tropics, huge numbers of waterfowl can be seen around drying waterholes towards the end of the dry season. They are strong flyers, however, and can travel long distances to escape the effects of drought.
Most waterfowl nest in tree forks or in hollows lined with down. Larger species, such as geese and swans, build nests on the ground or in floating vegetation.
The Black Swan, Australia's only native swan, is commonly found in every type of wetland in eastern and south-western Australia. Swans usually feed by up-ending their bodies and grazing underwater to a depth of about one metre.
The Magpie Goose is common in freshwater habitats in northern Australia and large flocks can descend on feeding grounds. This sometimes means that crops are destroyed. As a result, the bird is often singled out to be shot by farmers and hunters. The Cape Barren Goose was also once a target as it was thought to compete with livestock for pasture. Found on islands and coastal grasslands in Tasmania and southern Australia, it is now a protected species.
Ducks feed in many different ways. Most Australian ducks are 'dabblers', that is, they up-end their bodies in shallow water and feed along the bottom. Other species, such as the Musk Duck and the Blue-billed Duck, dive underwater for food. The Pink-eared Duck feeds on the surface, draining water through its bill to search for small items of food. Some species, such as whistling ducks, both dabble and dive.
Migrating waders need to roost and feed before and after their long flights between Australia and South-East Asia. If their usual nesting and feeding places are destroyed, the birds must find new ones. This is not always easy. Already vast areas of mangrove forest and mudflats have been destroyed on both continents to make way for agriculture, housing or industry. Other factors also threaten the habitat of water birds:
- Domestic stock can muddy waterholes, often making them unsuitable for water birds. This can be a real problem in drier parts of Australia.
- In northern Australia, feral buffalo can break down natural land banks that separate fresh and salty water. Saltwater can kill the freshwater vegetation on which water birds rely.
- Increased tourism and the build-up of urban areas lead to the use of wetlands for boating and water sports, discouraging water birds.
- Industrial waste, especially near large cities, has made many once rich feeding sites unsuitable for all but a few hardy water bird species.
Waders are a traditional food source in many Asian countries. It is estimated that between 0.25 and 1.5 million waders are killed there each year when the birds migrate from Australia. Several wader species were also once hunted for food and sport in Australia.
So far, there is no evidence that hunting is likely to cause the extinction of any waterfowl species found in Australia today. But this does not mean that protective measures are not needed. In most States, surveys of bird populations are held before each hunting season. Authorities use this information to decide whether to limit or ban the shooting of certain species or even to close certain areas for the season.
Conservationists have another growing concern: waterfowl that use wetlands popular with hunters may become poisoned by swallowing the lead shot that has built up in the bottom of waterways.
Of course, people are not the only hunters of water birds. Introduced predators, such as foxes and feral cats, take a toll on all bird species, especially their young.