Fewer Arctic wader birds seen in Australia
The migration of arctic wading birds from the northern hemisphere to the wetlands of southern Australia has slumped massively in the past three decades.
Dr David Paton from the University of Adelaide said a survey of the birds in January revealed that numbers had dropped to 15,000 compared to 250,000 in the 1960s. The birds have been here since about August and are now commencing the long return flight north.
The disappearance of the arctic visitors, which include the red-necked stint, sharp-tailed sandpiper and curlew sandpiper has puzzled scientists, but the finger is being pointed at dramatic changes in local waterways.
When the birds come from Alaska to winter in Australia, they make a beeline for The Coorong, a long series of lagoons which stretches south from the mouth of the Murray River in South Australia.
Less than 3km wide, it separates the Southern Ocean and Younghusband Peninsula. The 47,000 hectares are home to about 90 species of waterbirds and shore birds, 21 species of seabirds, 33 species of birds that migrate annually from the northern hemisphere and 14 protected species.
The Murray Darling River system, which feeds The Coorong has been massively altered in the past few decades. Substantial amounts have been diverted for agriculture, and the flow is artificially regulated by water releases.
As a result, less than 20 per cent of the water from the system now flows out its mouth. Interestingly, it's not just the change in the volume of water which affects the birds but changes in the sand.
Originally, says Dr Paton, the sand in which wader birds foraged used to wash down from upstream and was soft, allowing easy digging for worms and shells. Now the low river flows mean that much of the sand is washing in from the sea, which is much coarser in texture making it harder for the birds to extract their food.
"But changes going on overseas may also have a lot to do with it - it could be that much of the flyway has been affected, such as clearing of mangroves," he said. Dr Paton added that predation of birds by humans living in countries en route may also have increased in recent decades.