Birdwatchers each spring trudge out to mudflat and saltmarsh in search of the “Cinderellas” of the bird world – the migratory shorebirds that usually hide from view in inaccessible and sometimes remote wetlands.
The shorebirds, also termed waders, turn up on Australian shores in late August and early September after flying from breeding grounds at the top of the world.
The waders are eagerly awaited but each year fewer and fewer of these remarkable long-distance flyers hit our shores.
Two of the species known for their remarkable trans-continental journeys linking Tasmania with the far northern hemisphere have already been declared “extirpated” in Tasmania – the once familiar curlew sandpiper and the less common great knot. Others have seen populations reduced by up to 90 per cent in recent years.
Although the decline is occurring on all Australian coastlines, in Tasmania it is felt most noticeably. Tasmania is at the end of the East Asian-Australasian Flyway and any fall in bird numbers always shows up first at the extremity of their range.
Although wader experts accept that mortality has always been high among a group of birds that make a perilous 29,000 kilometre round-trip each year, current declines are unsustainable. Some waders breed within the Arctic Circle and one species, the bar-tailed godwit, has been recorded flying non-stop up to 11,000 kilometres on its southern flight from refuelling stops on the mudflats of the Yellow Sea in China.
The godwit is still to be found on the Sorell mudflats during our summer but another of the largest waders – the eastern curlew, magpie-sized with long curved bill – is now difficult to find. It once flew in such numbers that flocks blackened the sky over Sorell, where it was hunted for the pot.
Birdlife Tasmania has been monitoring wader numbers for more than 50 years – the oldest avian data sets in Australia – and these show the curlew is down by more than 90 per cent in number.
Another six waders show drops ranging from 35 to nearly 90 per cent.
In all, about 25 wader species visit Tasmania from the north and all show sharp declines although some have been traditionally rare at the furthest point of their range.
Vanishing habitat along the flyway, especially in south-east Asia where wetlands have made way for industrial, agricultural and housing development, is largely blamed for the wader catastrophe.
But development schemes that affect wetlands are not just confined to Asian countries. Development around Australia’s coastline is also impacting wader numbers, denying shorebirds places to rest and built fat and muscle for their return flights.
It has been argued that global wader conservation is out of Australia’s hands because the main threats to shorebird habitat have been centred on south-east Asia, especially China. The Chinese government, however, has come to the party in recent years, agreeing to protect existing wetlands.