The wetlands of southern Tasmania have been described as the “litmus test” for rapidly decreasing migratory shorebird populations across their range and a look at BirdLife Tasmania’s surveys proves the point.
The local affiliate of the national bird conservation body, BirdLife Australia, has the oldest data sets of shorebird populations and their records spanning more than half a century highlight the catastrophe enmeshing our wading birds.
A presentation by a Birdlife Tasmania researcher, Mike Newman, earlier this year revealed that local populations of the eastern curlew – the largest wader – had fallen by 90 per cent since the first surveys started in 1964.
Because southern Tasmania is at the far south of the migratory waders’ range falls in populations are noticed here first when the birds arrive from northern breeding grounds which, in some cases, are within the Arctic Circle.
It was after these initial surveys that the “litmus test” phrase was coined to describe how Tasmania would become a pointer to things to come. And so it has proven.
In his presentation, Mike Newman revealed other staggering losses in Tasmanian shorebirds populations. Along with the curlews, the red knot and sharp-tailed sandpiper have also decreased by 90 per cent. Other falling numbers include: red-necked stint (85%), Pacific golden plover (60%), bar-tailed godwit (50%), and greenshank (35%)
The migratory shorebirds travel vast distances from north to south on what is called the South East Asian-Australasian Flyway which has not only Tasmania as its southern-most limit but the shores of southern New Zealand.
A vital component of the flyway are the wetlands of the Yellow Sea between the two Koreas and China and in recent years these have seen unprecedented reclamation schemes turning mudflats and marshes into farms and industrial and housing development.
The loss of the wetlands has denied the shorebirds the crabs and other invertebrate food they need to supply the energy needed to continue their journeys.
But as Newman pointed out, the loss of feeding sites also affects the birds in their non-breeding ranges during our summer months.
Wetlands are not only being eroded by coastal development but by sea-level rise. To exacerbate matters, on roosting sites shorebirds are also being disturbed by increased human recreational activity. After feeding, the birds need to rest on mudflats and sandbanks above the high tide mark to build fat reserves to fuel the journeys north.
These migratory species display remarkable feats of endurance, as the results of recent satellite tracking has revealed.
The eastern curlew, for instance, flies nonstop to the Yellow Sea from Australia. Then, after re-fuelling, it flies on nonstop to is breeding grounds in Siberia.
The chicken-sized curlew, with a long, curved beak like that of an ibis, once flew in its tens of thousands across southern Tasmania. It was even shot for the pot on the mudflats surrounding Sorrell but it is now only counted in the tens, if any can be found at all.