MY biggest bird-watching moment during the summer months just past came with the sight of no less than 12 of the most dramatic of shorebirds, eastern curlew, feeding in mudflats near Midway Point.
My delight at seeing the biggest of the waders, however, was tempered by the realisation that I might never again see curlews in Tasmanian waters.
Numbers of eastern curlews reaching Tasmania – and indeed many other species of wader – are in freefall and the curlew was last year placed on the critically endangered list, along with another migratory shorebird, the curlew-sandpiper.
There are many reasons for the decline in numbers but in recent months the biggest factor affecting wader migration has been confirmed – the mass reclamation of mudflats and wetlands bordering and within the Yellow Sea in Asia.
The once vast wetlands are a vital staging post for waders making the journey from the far north – some from breeding grounds within the Arctic circle – to the far south of their range, southern Tasmania.
It has long been asserted that developments on the Chinese and Korean coasts of the Yellow Sea have been disastrous for populations of migratory shorebirds which fly through the region. Now recent research has eliminated numerous other causes of the population collapses which have been recorded recently in the shorebirds which fly along the migration route, called the East Asian-Australasian Flyway.
It just so happens the flyway crosses one of the most densely-populated regions of the world. Land is in short supply for housing, industrial development and agriculture and in the last 50 years developers have increasingly initiated programs to drain the Yellow Sea wetlands. These areas are viewed as wasted space in human terms, ripe for reclamation and development, or even for the dumping of rubbish.
Unfortunately, this reclamation destroys habitat crucial to the survival of millions of resident and migratory shorebirds. Mudflat sediments are rich in invertebrate life which is the primary food of the shorebirds. When the birds migrate, they expend a huge amount of energy along the way, and so must stop off at sites like the Yellow Sea to replenish that lost energy and that means eating as much as they can, as quickly as they can, so they can continue on their marathon journeys.
Extensive banding of shorebirds by the Australasian Wader Studies Group over the last few decades has allowed scientists to monitor the movements of these birds and this alerted conservationists to their plight.
Using this information, international birdlife researchers have established conclusively the decline in populations has been due to a significant loss of habitat in East Asia, and not factors in their breeding or wintering grounds.
The decline is being felt keenly in Tasmania. BirdLife Tasmania has 50-year records showing the population of eastern curlews reaching Tasmania has decreased 90 per cent in this time. Some years they are rarely seen, when half a century ago they flew in flocks so thick they were shot for the pot.